We describe spinal myoclonus in a 35-year-old homosexual man with concurrent human T-cell lymphotropic virus type III/lymphadenopathy--associated virus (HTLV III/LAV) infection of the central nervous system as indicated by intra-blood-brain barrier synthesis of HTLV III/LAV-specific IgG. The spinal myoclonus was characterized by asymmetric, rhythmic contractions of the abdomen with a frequency ranging between 40 and 70 per minute. The myoclonus was self-limited, resolving over the course of two months. Human T-cell lymphotropic virus type III/lymphadenopathy--associated virus should be considered among the viral causes of spinal myoclonus.