diff --git a/README.md b/README.md
index 468efd8..cebd853 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,9 @@ In the .soliumrc.json file, add:
         "zeppelin/no-unused-imports": [
           "warning"
         ],
+        "zeppelin/private-state-variables-underscore-prefix": [
+          "warning"
+        ],
         "zeppelin/all-state-variables-private": [
           "warning"
         ]
diff --git a/index.js b/index.js
index 7417417..001875f 100644
--- a/index.js
+++ b/index.js
@@ -18,6 +18,7 @@ module.exports = {
         "no-state-variable-shadowing": require("./rules/no-state-variable-shadowing"),
         "no-unchecked-send": require("./rules/no-unchecked-send"),
         "no-unused-imports": require("./rules/no-unused-imports"),
+        "private-state-variables-underscore-prefix": require("./rules/private-state-variables-underscore-prefix"),
         "all-state-variables-private": require("./rules/all-state-variables-private")
     }
 };
diff --git a/rules/private-state-variables-underscore-prefix.js b/rules/private-state-variables-underscore-prefix.js
new file mode 100644
index 0000000..ee01376
--- /dev/null
+++ b/rules/private-state-variables-underscore-prefix.js
@@ -0,0 +1,38 @@
+/**
+ * @fileoverview Report private state variables without underscore prefix.
+ */
+
+"use strict";
+
+module.exports = {
+    meta: {
+        docs: {
+            recommended: true,
+            type: "warning",
+            description: "Report private state variables without underscore prefix"
+        },
+        schema: []
+    },
+
+    create: function(context) {
+
+        function inspectStateVariableDeclaration(emitted) {
+            if (emitted.exit) {
+                return;
+            }
+            let stateVariable = emitted.node.name;
+            if ((stateVariable.charAt(0) !== "_") &&
+                    (emitted.node.visibility == "private")) {
+                context.report({
+                    node: emitted.node,
+                    message: `'${stateVariable}' does not have an underscore as prefix.`
+                });
+            }
+
+        }
+
+        return {
+            StateVariableDeclaration: inspectStateVariableDeclaration
+        };
+    }
+};
diff --git a/test/private-state-variables-underscore-prefix.js b/test/private-state-variables-underscore-prefix.js
new file mode 100644
index 0000000..0ee22c3
--- /dev/null
+++ b/test/private-state-variables-underscore-prefix.js
@@ -0,0 +1,95 @@
+/**
+ * @fileoverview Tests for private-state-variables-underscore-prefix
+ */
+
+"use strict";
+
+const dedent = require("dedent");
+const Solium = require("solium");
+const wrappers = require("./utils/wrappers");
+const addPragma = wrappers.addPragma;
+
+const userConfig = {
+    rules: {
+        "zeppelin/private-state-variables-underscore-prefix": 1
+    }
+};
+
+describe("[RULE] private-state-variables-underscore-prefix: Rejections", function() {
+
+    afterEach(function(done) {
+        Solium.reset();
+        done();
+    });
+
+    it("should reject private state variables without underscore prefix", function(done) {
+        const code = dedent`
+            contract TestContract {
+                bool private variableWithoutUnderscorePrefix = false;
+            }`,
+            errors = Solium.lint(addPragma(code), userConfig);
+
+        errors.should.be.instanceof(Array);
+        errors.length.should.equal(1);
+        errors[0].message.should.equal(
+            "'variableWithoutUnderscorePrefix' does not have an underscore as prefix.");
+        done();
+    });
+});
+
+describe("[RULE] private-state-variables-underscore-prefix: Acceptances", function() {
+
+    afterEach(function(done) {
+        Solium.reset();
+        done();
+    });
+
+    it("should accept private state variables with underscore prefix", function(done) {
+        const code = dedent`
+            contract TestContract {
+                bool private _variableWithUnderscorePrefix = false;
+            }`,
+            errors = Solium.lint(addPragma(code), userConfig);
+
+        errors.should.deepEqual([]);
+
+        done();
+    });
+
+    it("should accept public state variables", function(done) {
+        const code = dedent`
+            contract TestContract {
+                bool public publicStateVariable = false;
+            }`,
+            errors = Solium.lint(addPragma(code), userConfig);
+
+        errors.should.deepEqual([]);
+
+        done();
+    });
+
+    it("should accept internal state variables", function(done) {
+        const code = dedent`
+            contract TestContract {
+                bool internal internalStateVariable = false;
+            }`,
+            errors = Solium.lint(addPragma(code), userConfig);
+
+        errors.should.deepEqual([]);
+
+        done();
+    });
+
+    it("should accept state variables with default visibility", function(done) {
+        const code = dedent`
+            contract TestContract {
+                bool stateVariableWithDefaultVisibility = false;
+            }`,
+            errors = Solium.lint(addPragma(code), userConfig);
+
+        errors.should.deepEqual([]);
+
+        done();
+    });
+
+});