Neuromuscular diseases are common in acquired immune deficiency syndrome (AIDS). Although the clinical incidence of peripheral neuropathy has not been systematically studied, various reports suggest that up to 40% of AIDS patients have clinical symptoms. Biopsy and autopsy studies have shown an inflammatory neuropathy with a variable component of demyelination and axonal loss. Evidence of direct involvement by the human immunodeficiency virus (HIV) is scant. Immunosuppression followed by cytomegalovirus (CMV) infection appears to be a direct cause of polyradiculoneuropathy and perhaps other forms of peripheral neuropathy in AIDS. The clinical incidence of myopathy in AIDS is less clear, and clinically less appreciated than the neuropathy. Scattered reports have identified an inflammatory myopathy that does not appear to be due to direct HIV infection, but could be mediated by another human retrovirus. HIV seropositive patients being treated with antiviral drugs develop a unique set of neuromuscular diseases that must be distinguished from the non-drug-related conditions.