diff --git a/stix2/properties.py b/stix2/properties.py
index b638f5f..0b52544 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -1,5 +1,6 @@
 import re
 import uuid
+import sys
 
 
 class Property(object):
@@ -72,21 +73,66 @@ class Property(object):
         return value
 
 
-class List(Property):
+class ListProperty(Property):
 
     def __init__(self, contained):
         """
         contained should be a type whose constructor creates an object from the value
         """
-        self.contained = contained
+        if contained == StringProperty:
+            self.contained = StringProperty().string_type
+        elif contained == BooleanProperty:
+            self.contained = bool
+        else:
+            self.contained = contained
 
     def validate(self, value):
-        # TODO: ensure iterable
-        for item in value:
-            self.contained.validate(item)
+        try:
+            list_ = self.clean(value)
+        except ValueError:
+            raise
+
+        if len(list_) < 1:
+            raise ValueError("must not be empty.")
+
+        try:
+            for item in list_:
+                self.contained.validate(item)
+        except ValueError:
+            raise
+        except AttributeError:
+            # type of list has no validate() function (eg. built in Python types)
+            # TODO Should we raise an error here?
+            pass
+
+        return list_
 
     def clean(self, value):
         return [self.contained(x) for x in value]
+        try:
+            return [self.contained(x) for x in value]
+        except TypeError:
+            raise ValueError("must be an iterable over a type whose constructor creates an object from the value.")
+
+
+class StringProperty(Property):
+
+    def __init__(self):
+        if sys.version_info[0] == 2:
+            self.string_type = unicode
+        else:
+            self.string_type = str
+        super(StringProperty, self).__init__()
+
+    def clean(self, value):
+        return self.string_type(value)
+
+    def validate(self, value):
+        try:
+            val = self.clean(value)
+        except ValueError:
+            raise
+        return val
 
 
 class TypeProperty(Property):
diff --git a/stix2/test/test_properties.py b/stix2/test/test_properties.py
index a210302..22a6b44 100644
--- a/stix2/test/test_properties.py
+++ b/stix2/test/test_properties.py
@@ -1,7 +1,8 @@
 import pytest
 
-from stix2.properties import (Property, BooleanProperty, IDProperty,
-                              ReferenceProperty, TypeProperty)
+from stix2.properties import (Property, BooleanProperty, ListProperty,
+                              StringProperty, TypeProperty, IDProperty,
+                              ReferenceProperty)
 
 
 def test_property():
@@ -50,6 +51,22 @@ def test_fixed_property():
     assert p.validate(p.default())
 
 
+def test_list_property():
+    p = ListProperty(StringProperty)
+
+    assert p.validate(['abc', 'xyz'])
+    with pytest.raises(ValueError):
+        p.validate([])
+
+
+def test_string_property():
+    prop = StringProperty()
+
+    assert prop.validate('foobar')
+    assert prop.validate(1)
+    assert prop.validate([1, 2, 3])
+
+
 def test_type_property():
     prop = TypeProperty('my-type')