Strongyloides stercoralis, the only helminthic parasite that can complete its life cycle in the human host, is also the only helminthic parasite that has been reported with any frequency in AIDS patients. Symptoms include hives, skin eruptions, abdominal pain, perianal pruitis, diarrhea, and pneumonitis. Diagnosis is made by demonstrating rhabditiform larvae in the stool or female parasitic worms and eggs in the small intestinal mucosa; in disseminated cases, rhabditiform or filariform larvae can be found in liver, heart, lungs, thyroid, kidneys, adrenals, pancreas, lymph nodes, and central nervous system. Successful treatment has been achieved with thiabendazol. Strongyloidiasis is uncommon, but since cell-mediated immunity is important in combatting this organism, and since T-lymphocyte function is impaired in AIDS patients, strongyloidiasis should not be overlooked in the diagnosis of opportunistic illnesses in these individuals.