diff --git a/.eslintignore b/.eslintignore
new file mode 100644
index 0000000000..a01f2dcfa2
--- /dev/null
+++ b/.eslintignore
@@ -0,0 +1,2 @@
+/dist
+
diff --git a/.gitignore b/.gitignore
index ad46b30886..366ec9d174 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,3 +59,6 @@ typings/
 
 # next.js build output
 .next
+
+# dist
+dist/
diff --git a/index-commonjs.js b/index-commonjs.js
deleted file mode 100644
index 2ffe66a8c0..0000000000
--- a/index-commonjs.js
+++ /dev/null
@@ -1,42 +0,0 @@
-'use strict';
-
-// Copyright (C) 2011 Google Inc.
-// Copyright (C) 2018 Agoric
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-/**
- * Is allegedNum a number in the contiguous range of exactly and
- * unambiguously representable natural numbers (non-negative integers)?
- *
- * <p>See <a href=
- * "https://code.google.com/p/google-caja/issues/detail?id=1801"
- * >Issue 1801: Nat must include at most (2**53)-1</a>
- * and <a href=
- * "https://mail.mozilla.org/pipermail/es-discuss/2013-July/031716.html"
- * >Allen Wirfs-Brock's suggested phrasing</a> on es-discuss.
- */
-
-function Nat(allegedNum) {
-  if (!Number.isSafeInteger(allegedNum)) {
-    throw new RangeError('not a safe integer');
-  }
-
-  if (allegedNum < 0) {
-    throw new RangeError('negative');
-  }
-
-  return allegedNum;
-}
-
-module.exports = Nat;
diff --git a/package-lock.json b/package-lock.json
index 74c6727ec7..a335f1fabe 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -640,6 +640,12 @@
       "integrity": "sha512-qzm/XxIbxm/FHyH341ZrbnMUpe+5Bocte9xkmFMzPMjRaZMcXww+MpBptFvtU+79L362nqiLhekCxCxDPaUMBQ==",
       "dev": true
     },
+    "esm": {
+      "version": "3.2.7",
+      "resolved": "https://registry.npmjs.org/esm/-/esm-3.2.7.tgz",
+      "integrity": "sha512-zsyD5gO8CY9dpK3IrdC4WHtvtHGXEFOpYA4zB+6p+Kygf3vv/6kF3YMEQLOArwKPPNvKt8gjI8UYhQW8bXM/YQ==",
+      "dev": true
+    },
     "espree": {
       "version": "4.1.0",
       "resolved": "https://registry.npmjs.org/espree/-/espree-4.1.0.tgz",
diff --git a/package.json b/package.json
index f99e7d39f4..5c7018c2f2 100644
--- a/package.json
+++ b/package.json
@@ -2,11 +2,12 @@
   "name": "@agoric/nat",
   "version": "2.0.0",
   "description": "Ensures that a number is within the natural numbers (0, 1, 2...) or throws a RangeError",
-  "main": "index-commonjs.js",
-  "module": "index.js",
+  "main": "dist/nat.cjs.js",
+  "module": "dist/nat.esm.js",
+  "browser": "dist/nat.umd.js",
   "scripts": {
-    "test": "node test/test.js",
-    "create-cjs": "rollup index.js --file index-commonjs.js --format cjs",
+    "test": "node -r esm test/test.js",
+    "build": "rollup -c",
     "lint-fix": "eslint --fix '**/*.{js,jsx}'",
     "lint-check": "eslint '**/*.{js,jsx}'"
   },
@@ -29,6 +30,7 @@
     "eslint-plugin-jsx-a11y": "^6.2.1",
     "eslint-plugin-prettier": "^3.0.1",
     "eslint-plugin-react": "^7.12.4",
+    "esm": "^3.2.7",
     "prettier": "1.16.4",
     "rollup": "^1.1.2",
     "tape": "^4.9.2"
@@ -40,5 +42,8 @@
     "integer",
     "int",
     "overflow"
+  ],
+  "files": [
+    "dist"
   ]
 }
diff --git a/rollup.config.js b/rollup.config.js
new file mode 100644
index 0000000000..82c1442fc1
--- /dev/null
+++ b/rollup.config.js
@@ -0,0 +1,20 @@
+export default [
+  {
+    input: 'src/index.js',
+    output: [
+      {
+        file: 'dist/nat.umd.js',
+        format: 'umd',
+        name: 'Nat',
+      },
+      {
+        file: 'dist/nat.esm.js',
+        format: 'esm',
+      },
+      {
+        file: 'dist/nat.cjs.js',
+        format: 'cjs',
+      },
+    ],
+  },
+];
diff --git a/index.js b/src/index.js
similarity index 100%
rename from index.js
rename to src/index.js
diff --git a/test/test.js b/test/test.js
index f5fd9a012a..e375761eb5 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,7 +1,7 @@
 /* eslint no-mixed-operators: "off" */
 
-const test = require('tape');
-const Nat = require('../index-commonjs.js');
+import test from 'tape';
+import Nat from '../src/index';
 
 test('Nat() throws when not a natural number', t => {
   t.equal(Nat(0), 0);