diff --git a/pylink/jlock.py b/pylink/jlock.py
index b08114a..049097b 100644
--- a/pylink/jlock.py
+++ b/pylink/jlock.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import psutil
+from . import util
 
 import errno
 import tempfile
@@ -103,7 +103,7 @@ def acquire(self):
 
                 # In the case that the lockfile exists, but the pid does not
                 # correspond to a valid process, remove the file.
-                if not psutil.pid_exists(pid):
+                if not util.pid_exists(pid):
                     os.remove(self.path)
 
             except ValueError as e:
diff --git a/pylink/util.py b/pylink/util.py
index d9216a3..394c2b4 100644
--- a/pylink/util.py
+++ b/pylink/util.py
@@ -17,6 +17,8 @@
 
 import platform
 import sys
+import os
+import ctypes
 
 
 def is_integer(val):
@@ -180,3 +182,64 @@ def calculate_parity(n):
         y += n & 1
         n = n >> 1
     return y & 1
+
+
+def pid_exists_win32(pid):
+    ERROR_ACCESS_DENIED = 0x5
+    ERROR_INVALID_PARAMETER = 0x57
+    PROCESS_QUERY_LIMITED_INFORMATION = 0x1000
+    STILL_ACTIVE = 0x103
+
+    if pid == 0:
+        return True
+    elif pid == -1:
+        return False
+
+    hProcess = ctypes.windll.kernel32.OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, False, pid)
+    if not hProcess:
+        error = ctypes.windll.kernel32.GetLastError()
+        if error == ERROR_ACCESS_DENIED:
+            return True
+        elif error == ERROR_INVALID_PARAMETER:
+            return False
+        else:
+            raise ctypes.WinError()
+
+    exitCode = ctypes.c_int(0)
+    pExitCode = ctypes.pointer(exitCode)
+    if not ctypes.windll.kernel32.GetExitCodeProcess(hProcess, pExitCode):
+        error = ctypes.windll.kernel32.GetLastError()
+        if error == ERROR_ACCESS_DENIED:
+            ctypes.windll.kernel32.CloseHandle(hProcess)
+            return True
+        else:
+            raise ctypes.WinError()
+
+    if exitCode.value == STILL_ACTIVE:
+        ctypes.windll.kernel32.CloseHandle(hProcess)
+        return True
+
+    ctypes.windll.kernel32.CloseHandle(hProcess)
+    return False
+
+
+def pid_exists_posix(pid):
+    if pid == 0:
+        return True
+    elif pid < 0:
+        return False
+
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    except PermissionError:
+        return True
+    return True
+
+
+def pid_exists(pid):
+    if sys.platform.startswith('win') or sys.platform.startswith('cygwin'):
+        return pid_exists_win32(pid)
+    else:
+        return pid_exists_posix(pid)
diff --git a/requirements.txt b/requirements.txt
index fa7e8ea..fa39b41 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,6 @@
 behave == 1.2.5
 coverage == 4.4.1
 future
-psutil >= 5.2.2
 pycodestyle >= 2.3.1
 six
 sphinx == 1.4.8
diff --git a/setup.py b/setup.py
index bb09e58..aa3d2bd 100644
--- a/setup.py
+++ b/setup.py
@@ -14,13 +14,6 @@
 
 import sys
 
-# Stub the 'psutil' module that is required by this package in order to enable
-# the main module to be imported.
-try:
-    import psutil
-except ImportError:
-    sys.modules['psutil'] = {}
-
 import pylink
 
 import os
@@ -255,7 +248,6 @@ def long_description():
 
     # Dependencies.
     install_requires=[
-        'psutil >= 5.2.2',
         'future',
         'six'
     ],
diff --git a/tests/unit/test_jlock.py b/tests/unit/test_jlock.py
index 7913b86..392b8aa 100644
--- a/tests/unit/test_jlock.py
+++ b/tests/unit/test_jlock.py
@@ -74,7 +74,7 @@ def test_jlock_init_and_delete(self):
     @mock.patch('os.open')
     @mock.patch('os.write')
     @mock.patch('os.remove')
-    @mock.patch('pylink.jlock.psutil')
+    @mock.patch('pylink.jlock.util')
     @mock.patch('pylink.jlock.open')
     def test_jlock_acquire_exists(self, mock_open, mock_util, mock_rm, mock_wr, mock_op, mock_exists, mock_close):
         """Tests trying to acquire when the lock exists for an active process.
@@ -82,7 +82,7 @@ def test_jlock_acquire_exists(self, mock_open, mock_util, mock_rm, mock_wr, mock
         Args:
           self (TestJLock): the ``TestJLock`` instance
           mock_open (Mock): mocked built-in open method
-          mock_util (Mock): mocked ``psutil`` module
+          mock_util (Mock): mocked ``util`` module
           mock_rm (Mock): mocked os remove method
           mock_wr (Mock): mocked os write method
           mock_op (Mock): mocked os open method
@@ -122,7 +122,7 @@ def test_jlock_acquire_exists(self, mock_open, mock_util, mock_rm, mock_wr, mock
     @mock.patch('os.open')
     @mock.patch('os.write')
     @mock.patch('os.remove')
-    @mock.patch('pylink.jlock.psutil')
+    @mock.patch('pylink.jlock.util')
     @mock.patch('pylink.jlock.open')
     def test_jlock_acquire_os_error(self, mock_open, mock_util, mock_rm, mock_wr, mock_op, mock_exists, mock_close):
         """Tests trying to acquire the lock but generating an os-level error.
@@ -130,7 +130,7 @@ def test_jlock_acquire_os_error(self, mock_open, mock_util, mock_rm, mock_wr, mo
         Args:
           self (TestJLock): the ``TestJLock`` instance
           mock_open (Mock): mocked built-in open method
-          mock_util (Mock): mocked ``psutil`` module
+          mock_util (Mock): mocked ``util`` module
           mock_rm (Mock): mocked os remove method
           mock_wr (Mock): mocked os write method
           mock_op (Mock): mocked os open method
@@ -167,7 +167,7 @@ def test_jlock_acquire_os_error(self, mock_open, mock_util, mock_rm, mock_wr, mo
     @mock.patch('os.open')
     @mock.patch('os.write')
     @mock.patch('os.remove')
-    @mock.patch('pylink.jlock.psutil')
+    @mock.patch('pylink.jlock.util')
     @mock.patch('pylink.jlock.open')
     def test_jlock_acquire_bad_file(self, mock_open, mock_util, mock_rm, mock_wr, mock_op, mock_exists, mock_close):
         """Tests acquiring the lockfile when the current lockfile is invallid.
@@ -175,7 +175,7 @@ def test_jlock_acquire_bad_file(self, mock_open, mock_util, mock_rm, mock_wr, mo
         Args:
           self (TestJLock): the ``TestJLock`` instance
           mock_open (Mock): mocked built-in open method
-          mock_util (Mock): mocked ``psutil`` module
+          mock_util (Mock): mocked ``util`` module
           mock_rm (Mock): mocked os remove method
           mock_wr (Mock): mocked os write method
           mock_op (Mock): mocked os open method
@@ -216,7 +216,7 @@ def test_jlock_acquire_bad_file(self, mock_open, mock_util, mock_rm, mock_wr, mo
     @mock.patch('os.open')
     @mock.patch('os.write')
     @mock.patch('os.remove')
-    @mock.patch('pylink.jlock.psutil')
+    @mock.patch('pylink.jlock.util')
     @mock.patch('pylink.jlock.open')
     def test_jlock_acquire_invalid_pid(self, mock_open, mock_util, mock_rm, mock_wr, mock_op, mock_exists, mock_close):
         """Tests acquiring the lockfile when the pid in the lockfile is invalid.
@@ -224,7 +224,7 @@ def test_jlock_acquire_invalid_pid(self, mock_open, mock_util, mock_rm, mock_wr,
         Args:
           self (TestJLock): the ``TestJLock`` instance
           mock_open (Mock): mocked built-in open method
-          mock_util (Mock): mocked ``psutil`` module
+          mock_util (Mock): mocked ``util`` module
           mock_rm (Mock): mocked os remove method
           mock_wr (Mock): mocked os write method
           mock_op (Mock): mocked os open method
@@ -263,7 +263,7 @@ def test_jlock_acquire_invalid_pid(self, mock_open, mock_util, mock_rm, mock_wr,
     @mock.patch('os.open')
     @mock.patch('os.write')
     @mock.patch('os.remove')
-    @mock.patch('pylink.jlock.psutil')
+    @mock.patch('pylink.jlock.util')
     @mock.patch('pylink.jlock.open')
     def test_jlock_acquire_old_pid(self, mock_open, mock_util, mock_rm, mock_wr, mock_op, mock_exists, mock_close):
         """Tests acquiring when the PID in the lockfile does not exist.
@@ -271,7 +271,7 @@ def test_jlock_acquire_old_pid(self, mock_open, mock_util, mock_rm, mock_wr, moc
         Args:
           self (TestJLock): the ``TestJLock`` instance
           mock_open (Mock): mocked built-in open method
-          mock_util (Mock): mocked ``psutil`` module
+          mock_util (Mock): mocked ``util`` module
           mock_rm (Mock): mocked os remove method
           mock_wr (Mock): mocked os write method
           mock_op (Mock): mocked os open method