diff --git a/cryptography/hazmat/backends/openssl/backend.py b/cryptography/hazmat/backends/openssl/backend.py
index 4906646..284fa98 100644
--- a/cryptography/hazmat/backends/openssl/backend.py
+++ b/cryptography/hazmat/backends/openssl/backend.py
@@ -22,7 +22,7 @@
 )
 from cryptography.hazmat.primitives import interfaces
 from cryptography.hazmat.primitives.ciphers.algorithms import (
-    AES, Blowfish, Camellia, CAST5, TripleDES, ARC4,
+    AES, Blowfish, Camellia, TripleDES, ARC4,
 )
 from cryptography.hazmat.primitives.ciphers.modes import (
     CBC, CTR, ECB, OFB, CFB, GCM,
@@ -108,11 +108,6 @@
                 GetCipherByName("bf-{mode.name}")
             )
         self.register_cipher_adapter(
-            CAST5,
-            ECB,
-            GetCipherByName("cast5-ecb")
-        )
-        self.register_cipher_adapter(
             ARC4,
             type(None),
             GetCipherByName("rc4")
diff --git a/cryptography/hazmat/bindings/openssl/binding.py b/cryptography/hazmat/bindings/openssl/binding.py
index 2a1e118..8a4e1dd 100644
--- a/cryptography/hazmat/bindings/openssl/binding.py
+++ b/cryptography/hazmat/bindings/openssl/binding.py
@@ -13,9 +13,8 @@
 
 from __future__ import absolute_import, division, print_function
 
-from cryptography.hazmat.bindings.utils import (
-    build_ffi, binding_available
-)
+from cryptography.hazmat.bindings.utils import build_ffi
+
 
 _OSX_PRE_INCLUDE = """
 #ifdef __APPLE__
@@ -84,4 +83,5 @@
 
     @classmethod
     def is_available(cls):
-        return binding_available(cls._ensure_ffi_initialized)
+        # OpenSSL is the only binding so for now it must always be available
+        return True
diff --git a/cryptography/hazmat/bindings/utils.py b/cryptography/hazmat/bindings/utils.py
index 40fd07f..69290eb 100644
--- a/cryptography/hazmat/bindings/utils.py
+++ b/cryptography/hazmat/bindings/utils.py
@@ -87,11 +87,3 @@
                     delattr(lib, name)
 
     return ffi, lib
-
-
-def binding_available(initializer):
-    try:
-        initializer()
-        return True
-    except cffi.VerificationError:
-        return False
diff --git a/cryptography/hazmat/primitives/ciphers/algorithms.py b/cryptography/hazmat/primitives/ciphers/algorithms.py
index a5cfce9..19cf192 100644
--- a/cryptography/hazmat/primitives/ciphers/algorithms.py
+++ b/cryptography/hazmat/primitives/ciphers/algorithms.py
@@ -90,21 +90,6 @@
         return len(self.key) * 8
 
 
-@utils.register_interface(interfaces.BlockCipherAlgorithm)
-@utils.register_interface(interfaces.CipherAlgorithm)
-class CAST5(object):
-    name = "CAST5"
-    block_size = 64
-    key_sizes = frozenset(range(40, 129, 8))
-
-    def __init__(self, key):
-        self.key = _verify_key_size(self, key)
-
-    @property
-    def key_size(self):
-        return len(self.key) * 8
-
-
 @utils.register_interface(interfaces.CipherAlgorithm)
 class ARC4(object):
     name = "RC4"
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 59aff99..a683bb9 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -189,15 +189,6 @@
                       ``56`` bits long), they can simply be concatenated to
                       produce the full key. This must be kept secret.
 
-.. class:: CAST5(key)
-
-    CAST5 (also known as CAST-128) is a block cipher approved for use in the
-    Canadian government by their Communications Security Establishment. It is a
-    variable key length cipher and supports keys from 40-128 bits in length.
-
-    :param bytes key: The secret key, 40-128 bits in length (in increments of
-                      8).  This must be kept secret.
-
 Weak Ciphers
 ------------
 
diff --git a/tests/hazmat/bindings/test_bindings.py b/tests/hazmat/bindings/test_bindings.py
deleted file mode 100644
index 7af1d58..0000000
--- a/tests/hazmat/bindings/test_bindings.py
+++ /dev/null
@@ -1,32 +0,0 @@
-# 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.
-
-from __future__ import absolute_import, division, print_function
-
-import cffi
-
-from cryptography.hazmat.bindings.utils import binding_available
-from cryptography.hazmat.bindings.openssl.binding import Binding
-
-
-def dummy_initializer():
-    ffi = cffi.FFI()
-    ffi.verify(source="#include <fake_header.h>")
-
-
-def test_binding_available():
-    assert binding_available(Binding._ensure_ffi_initialized) is True
-
-
-def test_binding_unavailable():
-    assert binding_available(dummy_initializer) is False
diff --git a/tests/hazmat/primitives/test_cast5.py b/tests/hazmat/primitives/test_cast5.py
deleted file mode 100644
index d65a86b..0000000
--- a/tests/hazmat/primitives/test_cast5.py
+++ /dev/null
@@ -1,41 +0,0 @@
-# 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.
-
-from __future__ import absolute_import, division, print_function
-
-import binascii
-import os
-
-import pytest
-
-from cryptography.hazmat.primitives.ciphers import algorithms, modes
-
-from .utils import generate_encrypt_test
-from ...utils import load_nist_vectors
-
-
-@pytest.mark.supported(
-    only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.ECB()
-    ),
-    skip_message="Does not support CAST5 ECB",
-)
-@pytest.mark.cipher
-class TestCAST5(object):
-    test_ECB = generate_encrypt_test(
-        load_nist_vectors,
-        os.path.join("ciphers", "CAST5"),
-        ["cast5-ecb.txt"],
-        lambda key, **kwargs: algorithms.CAST5(binascii.unhexlify((key))),
-        lambda **kwargs: modes.ECB(),
-    )
diff --git a/tests/hazmat/primitives/test_ciphers.py b/tests/hazmat/primitives/test_ciphers.py
index 653f7ce..6a7b2f9 100644
--- a/tests/hazmat/primitives/test_ciphers.py
+++ b/tests/hazmat/primitives/test_ciphers.py
@@ -18,7 +18,7 @@
 import pytest
 
 from cryptography.hazmat.primitives.ciphers.algorithms import (
-    AES, Camellia, TripleDES, Blowfish, CAST5, ARC4
+    AES, Camellia, TripleDES, Blowfish, ARC4
 )
 
 
@@ -80,19 +80,6 @@
             Blowfish(binascii.unhexlify(b"0" * 6))
 
 
-class TestCAST5(object):
-    @pytest.mark.parametrize(("key", "keysize"), [
-        (b"0" * (keysize // 4), keysize) for keysize in range(40, 129, 8)
-    ])
-    def test_key_size(self, key, keysize):
-        cipher = CAST5(binascii.unhexlify(key))
-        assert cipher.key_size == keysize
-
-    def test_invalid_key_size(self):
-        with pytest.raises(ValueError):
-            CAST5(binascii.unhexlify(b"0" * 34))
-
-
 class TestARC4(object):
     @pytest.mark.parametrize(("key", "keysize"), [
         (b"0" * 10, 40),