diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index f9b0a2ae50abce5..512e88bebbea87d 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -13,6 +13,8 @@ Changes:
 
 - ``attr.asdict``\ 's ``dict_factory`` arguments is now propagated on recursion.
   `#45 <https://github.com/hynek/attrs/issues/45>`_
+- ``attr.asdict`` and ``attr.has`` are significantly faster.
+  `#48 <https://github.com/hynek/attrs/issues/48>`_
 
 
 ----
diff --git a/src/attr/_funcs.py b/src/attr/_funcs.py
index 07f4495dff80a95..a1461a35968d037 100644
--- a/src/attr/_funcs.py
+++ b/src/attr/_funcs.py
@@ -3,7 +3,7 @@
 import copy
 
 from ._compat import iteritems
-from ._make import Attribute, NOTHING, fields
+from ._make import Attribute, NOTHING, _fast_attrs_iterate
 
 
 def asdict(inst, recurse=True, filter=None, dict_factory=dict):
@@ -30,7 +30,7 @@ def asdict(inst, recurse=True, filter=None, dict_factory=dict):
     .. versionadded:: 16.0.0
         *dict_factory*
     """
-    attrs = fields(inst.__class__)
+    attrs = _fast_attrs_iterate(inst)
     rv = dict_factory()
     for a in attrs:
         v = getattr(inst, a.name)
@@ -71,12 +71,7 @@ def has(cl):
 
     :rtype: :class:`bool`
     """
-    try:
-        fields(cl)
-    except ValueError:
-        return False
-    else:
-        return True
+    return getattr(cl, "__attrs_attrs__", None) is not None
 
 
 def assoc(inst, **changes):
diff --git a/tests/test_funcs.py b/tests/test_funcs.py
index 7dc47dd193ec47f..d7b3193eb56ea56 100644
--- a/tests/test_funcs.py
+++ b/tests/test_funcs.py
@@ -15,12 +15,12 @@
 from attr._funcs import (
     asdict,
     assoc,
-    fields,
     has,
 )
 from attr._make import (
     attr,
     attributes,
+    fields,
 )
 
 MAPPING_TYPES = (dict, OrderedDict)