diff --git a/opentracing-api/src/lib.rs b/opentracing-api/src/lib.rs
index ac6ec50..4e3a842 100644
--- a/opentracing-api/src/lib.rs
+++ b/opentracing-api/src/lib.rs
@@ -3,7 +3,9 @@
 mod context;
 mod tag;
 mod field;
+mod span;
 
 pub use context::SpanContext;
-pub use tag::{ParseTagsError, Tags};
+pub use tag::{ParseTagsError, TagValue, Tags};
 pub use field::{Fields, ParseFieldsError};
+pub use span::Span;
diff --git a/opentracing-api/src/span.rs b/opentracing-api/src/span.rs
new file mode 100644
index 0000000..0570501
--- /dev/null
+++ b/opentracing-api/src/span.rs
@@ -0,0 +1,51 @@
+use SpanContext;
+use TagValue;
+
+/// The `Span` represents the OpenTracing specification's Span contract.
+pub trait Span<'a> {
+    /// The associated `SpanContext`.
+    type Context: SpanContext<'a>;
+
+    /// Retrieve the associated `SpanContext`.
+    ///
+    /// This may be called any time, including after `finish`.
+    fn context(&self) -> &'a Self::Context;
+
+    /// Sets a key:value tag on the `Span`.
+    fn set_tag(&mut self, key: &str, value: TagValue);
+
+    /// Record an event at the current walltime timestamp.
+    fn log(&mut self, event: String);
+
+    /// Record an event at the given walltime timestamp.
+    fn log_at(&mut self, timestamp: u64, event: String);
+
+    /// Sets a baggage item in the Span (and its SpanContext) as a key/value pair.
+    fn set_baggage_item(&mut self, key: &str, value: String);
+
+    /// the value of the baggage item identified by the given key, or None if no such item
+    /// could be found.
+    fn get_baggage_item(&self, key: &str) -> Option<&String>;
+
+    /// Sets the string name for the logical operation this span represents.
+    fn set_operation_name(&mut self, name: &str);
+
+    /// Returns the operation name if set, None otherwise.
+    fn get_operation_name(&self) -> Option<&'a str>;
+
+    /// Sets the end timestamp to now and finishes (records) the span.
+    ///
+    /// With the exception of calls to `context()`, this should be the last
+    /// call made to the span instance. Future calls to `finish` are defined
+    /// as noops, and future calls to other methods other than `context()`
+    /// lead to undefined behavior.
+    fn finish(&mut self);
+
+    /// Sets an explicit end timestamp and finishes (records) the span.
+    ///
+    /// With the exception of calls to `context()`, this should be the last
+    /// call made to the span instance. Future calls to `finish` are defined
+    /// as noops, and future calls to other methods other than `context()`
+    /// lead to undefined behavior.
+    fn finish_at(&mut self, timestamp: u64);
+}
diff --git a/opentracing-api/src/tag.rs b/opentracing-api/src/tag.rs
index 9f3123d..faaee88 100644
--- a/opentracing-api/src/tag.rs
+++ b/opentracing-api/src/tag.rs
@@ -171,6 +171,12 @@ impl fmt::Display for ParseTagsError {
     }
 }
 
+pub enum TagValue {
+    String(String),
+    Boolean(bool),
+    Number(f64),
+}
+
 #[cfg(test)]
 mod tests {