PURPOSE: To assess the patterns of abnormal neuroradiologic findings in patients with a hypercoagulable state related to activated protein C (APC) resistance. MATERIALS AND METHODS: Records in 23 patients with a hypercoagulable state related to APC resistance (18 women, five men; average age, 44.5 years) were reviewed for cerebrovascular disease risk factors and other causes of a hypercoagulable state. Computed tomographic scans, magnetic resonance (MR) images, angiograms, and transesophageal echocardiograms were also reviewed. RESULTS: Stroke risk factors or other causes of a hypercoagulable state were found in 12 patients. Arterial infarcts were seen in 18 patients. Hyperintense white matter foci were seen on MR images in six patients. Dural sinus thrombosis was found in four patients. Angiograms of intracranial circulation in six patients showed major artery occlusions in four. MR angiograms in four patients showed internal carotid artery occlusion in one. No major abnormalities were seen in extracranial cerebral vasculature in 15 patients. Transesophageal echocardiograms in 11 patients showed a patent foramen ovale in one patient but no systemic source of embolism. Seven patients had non-central nervous system thrombotic events. CONCLUSION: Patients with APC resistance and stroke appear to differ from the general stroke population in terms of age and frequency of extracranial sources of cerebrovascular disease.