diff --git a/R/onAttach.R b/R/onAttach.R
new file mode 100644
index 00000000..61b69dda
--- /dev/null
+++ b/R/onAttach.R
@@ -0,0 +1,22 @@
+
+.onAttach = function(libname, pkgname) {
+  if (!interactive()) {
+    return()
+  }
+  
+  threads_env <- Sys.getenv("R_RANGER_NUM_THREADS")
+  threads_option1 <- getOption("ranger.num.threads")
+  threads_option2 <- getOption("Ncpus")
+  
+  if (threads_env != "") {
+    thread_string <- paste(threads_env, "threads as set by environment variable R_RANGER_NUM_THREADS. Can be overwritten with num.threads.")
+  } else if (!is.null(threads_option1)) {
+    thread_string <- paste(threads_option1, "threads as set by options(ranger.num.threads = N). Can be overwritten with num.threads.")
+  } else if (!is.null(threads_option2)) {
+    thread_string <- paste(threads_option2, "threads as set by options(Ncpus = N). Can be overwritten with num.threads.")
+  } else {
+    thread_string <- "2 threads (default). Change with num.threads in ranger() and predict(), options(Ncpus = N), options(ranger.num.threads = N) or environment variable R_RANGER_NUM_THREADS."
+  }
+  
+  packageStartupMessage(paste("ranger", packageVersion("ranger"), "using", thread_string))
+}
diff --git a/R/predict.R b/R/predict.R
index 82599ab0..d11c453e 100644
--- a/R/predict.R
+++ b/R/predict.R
@@ -36,6 +36,9 @@
 ##' 
 ##' For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 ##' To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+##' 
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##'
 ##' @title Ranger prediction
 ##' @param object Ranger \code{ranger.forest} object.
@@ -45,7 +48,7 @@
 ##' @param type Type of prediction. One of 'response', 'se', 'terminalNodes', 'quantiles' with default 'response'. See below for details.
 ##' @param se.method Method to compute standard errors. One of 'jack', 'infjack' with default 'infjack'. Only applicable if type = 'se'. See below for details.
 ##' @param seed Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).
 ##' @param verbose Verbose output on or off.
 ##' @param inbag.counts Number of times the observations are in-bag in the trees.
 ##' @param ... further arguments passed to or from other methods.
@@ -193,7 +196,7 @@ predict.ranger.forest <- function(object, data, predict.all = FALSE,
   ## Num threads
   ## Default 0 -> detect from system in C++.
   if (is.null(num.threads)) {
-    num.threads = 0
+    num.threads <- as.integer(Sys.getenv("R_RANGER_NUM_THREADS", getOption("ranger.num.threads", getOption("Ncpus", 2L))))
   } else if (!is.numeric(num.threads) || num.threads < 0) {
     stop("Error: Invalid value for num.threads")
   }
@@ -433,6 +436,9 @@ predict.ranger.forest <- function(object, data, predict.all = FALSE,
 ##' 
 ##' For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 ##' To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+##' 
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##'
 ##' @title Ranger prediction
 ##' @param object Ranger \code{ranger} object.
@@ -444,7 +450,7 @@ predict.ranger.forest <- function(object, data, predict.all = FALSE,
 ##' @param quantiles Vector of quantiles for quantile prediction. Set \code{type = 'quantiles'} to use.
 ##' @param what User specified function for quantile prediction used instead of \code{quantile}. Must return numeric vector, see examples.
 ##' @param seed Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).
 ##' @param verbose Verbose output on or off.
 ##' @param ... further arguments passed to or from other methods.
 ##' @return Object of class \code{ranger.prediction} with elements
diff --git a/R/ranger.R b/R/ranger.R
index 51d64a9b..1cc11ff7 100644
--- a/R/ranger.R
+++ b/R/ranger.R
@@ -96,10 +96,10 @@
 ##' To use only the SNPs without sex or other covariates from the phenotype file, use \code{0} on the right hand side of the formula. 
 ##' Note that missing values are treated as an extra category while splitting.
 ##' 
-##' See \url{https://github.com/imbs-hl/ranger} for the development version.
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##' 
-##' With recent R versions, multithreading on Windows platforms should just work. 
-##' If you compile yourself, the new RTools toolchain is required.
+##' See \url{https://github.com/imbs-hl/ranger} for the development version.
 ##' 
 ##' @title Ranger
 ##' @param formula Object of class \code{formula} or \code{character} describing the model to fit. Interaction terms supported only for numerical variables.
@@ -133,7 +133,7 @@
 ##' @param quantreg Prepare quantile prediction as in quantile regression forests (Meinshausen 2006). Regression only. Set \code{keep.inbag = TRUE} to prepare out-of-bag quantile prediction.
 ##' @param time.interest Time points of interest (survival only). Can be \code{NULL} (default, use all observed time points), a vector of time points or a single number to use as many time points (grid over observed time points).
 ##' @param oob.error Compute OOB prediction error. Set to \code{FALSE} to save computation time, e.g. for large survival forests.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).
 ##' @param save.memory Use memory saving (but slower) splitting mode. No effect for survival and GWAS data. Warning: This option slows down the tree growing, use only if you encounter memory problems.
 ##' @param verbose Show computation status and estimated runtime.
 ##' @param node.stats Save node statistics. Set to \code{TRUE} to save prediction, number of observations and split statistics for each node.
@@ -523,7 +523,7 @@ ranger <- function(formula = NULL, data = NULL, num.trees = 500, mtry = NULL,
   ## Num threads
   ## Default 0 -> detect from system in C++.
   if (is.null(num.threads)) {
-    num.threads = 0
+    num.threads <- as.integer(Sys.getenv("R_RANGER_NUM_THREADS", getOption("ranger.num.threads", getOption("Ncpus", 2L))))
   } else if (!is.numeric(num.threads) || num.threads < 0) {
     stop("Error: Invalid value for num.threads")
   }
diff --git a/man/predict.ranger.Rd b/man/predict.ranger.Rd
index 362befca..2f9c63ac 100644
--- a/man/predict.ranger.Rd
+++ b/man/predict.ranger.Rd
@@ -38,7 +38,7 @@
 
 \item{seed}{Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.}
 
-\item{num.threads}{Number of threads. Default is number of CPUs available.}
+\item{num.threads}{Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).}
 
 \item{verbose}{Verbose output on or off.}
 
@@ -70,6 +70,9 @@ If \code{type = 'se'} is selected, the method to estimate the variances can be c
 
 For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+
+By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 }
 \examples{
 ## Classification forest
diff --git a/man/predict.ranger.forest.Rd b/man/predict.ranger.forest.Rd
index ba018b0e..805effda 100644
--- a/man/predict.ranger.forest.Rd
+++ b/man/predict.ranger.forest.Rd
@@ -33,7 +33,7 @@
 
 \item{seed}{Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.}
 
-\item{num.threads}{Number of threads. Default is number of CPUs available.}
+\item{num.threads}{Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).}
 
 \item{verbose}{Verbose output on or off.}
 
@@ -66,6 +66,9 @@ If \code{type = 'se'} is selected, the method to estimate the variances can be c
 
 For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+
+By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 }
 \references{
 \itemize{
diff --git a/man/ranger.Rd b/man/ranger.Rd
index 6b7465b8..9f8036b7 100644
--- a/man/ranger.Rd
+++ b/man/ranger.Rd
@@ -112,7 +112,7 @@ ranger(
 
 \item{oob.error}{Compute OOB prediction error. Set to \code{FALSE} to save computation time, e.g. for large survival forests.}
 
-\item{num.threads}{Number of threads. Default is number of CPUs available.}
+\item{num.threads}{Number of threads. Use 0 for all available cores. Default is 2 if not set by options/environment variables (see below).}
 
 \item{save.memory}{Use memory saving (but slower) splitting mode. No effect for survival and GWAS data. Warning: This option slows down the tree growing, use only if you encounter memory problems.}
 
@@ -230,10 +230,10 @@ All SNPs in the \code{GenABEL} object will be used for splitting.
 To use only the SNPs without sex or other covariates from the phenotype file, use \code{0} on the right hand side of the formula. 
 Note that missing values are treated as an extra category while splitting.
 
-See \url{https://github.com/imbs-hl/ranger} for the development version.
+By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 
-With recent R versions, multithreading on Windows platforms should just work. 
-If you compile yourself, the new RTools toolchain is required.
+See \url{https://github.com/imbs-hl/ranger} for the development version.
 }
 \examples{
 ## Classification forest with default settings