&NA;Two patients with altered hemostatic mechanisms developed spinal subarachnoid hemorrhage after difficult lumbar punctures. One patient had received anticoagulation therapy soon after lumbar puncture and the other had a low platelet count (63,000/mm3) at the time of lumbar puncture. In both patients a hematoma evolved, producing blockage of cerebrospinal fluid flow. Clinical manifestations consisted of severe back and radicular pain with sphincteric disturbances followed by rapidly developing severe paraparesis. Of the methods of radiographic evaluation that were used, including computed tomography (CT) without contrast enhancement, myelography, CT with intrathecally administered contrast medium, and magnetic resonance imaging, we found the best study to be myelography via lateral cervical puncture followed by CT. Unfortunately, diagnosis was delayed, and surgical evacuation of the hematomas did not substantially improve the patients' conditions. The salient clinical and radiographic features of this disorder and its pathophysiology are reviewed. Prompt recognition of these lesions is necessary so that surgical intervention may maximize chances of recovery. (Neurosurgery25:287‐293, 1989)