At autopsy, four homosexual men with acquired immunodeficiency syndrome (AIDS) were found to have selective degeneration of the gracile tract, a finding previously unreported in AIDS. Clinically, these patients had progressive lower extremity paresthesias and dysesthesias with reduced or absent ankle jerks, and eventually they developed dementia. Postmortem examination of spinal cords showed a striking loss of both axons and myelin sheaths confined to the fasciculus gracilis, with the most severe involvement in upper thoracic or cervical segments. Lumbar dorsal columns showed only a mild fiber loss, and no fiber loss was observed in lumbar dorsal roots. Lumbar dorsal root ganglia were available from one patient and showed a mild sensory ganglionitis. In all cases examined, microglial nodules were present in the brain. In 23 other individuals with AIDS who had autopsies consecutively with these four subjects, none had sensory neuropathy and the gracile tracts were normal. The combination of distal sensory neuropathy and gracile tract degeneration suggests a "dying-back" process of dorsal root ganglia neurons.