Cytomegalovirus (CMV) infection involving multiple organ systems is a common finding in the acquired immunodeficiency syndrome. Acute CMV neuritis was a complication in two patients with acquired immunodeficiency syndrome. The diagnosis was made in both patients at autopsy, where typical CMV inclusions in the lumbar dorsal roots were noted in one patient and the same inclusions were found in the retroperitoneal peripheral nerves in a second patient. Electron microscopy confirmed the presence of viral particles in affected nerve segments. Patient 1 was hospitalized for ascending motor paralysis that remained unexplained at the time of death. In patient 2 the finding of CMV neuritis was incidental. Although CMV infection has been cited as an event antecedent to acute inflammatory polyradiculopathy (Guillain-Barré syndrome), to our knowledge morphologic evidence of the presence of virus has not been documented in this disease previously.