Patients with AIDS are prone to develop infections caused by opportunistic pathogens. Unusual agents, such as Strongyloides stercoralis, are being described in this syndrome, resulting in disseminated disease which is always severe and, in some cases, fatal. We describe a case of a patient with AIDS and Strongyloides stercoralis infection involving the gastrointestinal tract and the lungs. Therapy with thiabendazole for ten days led to resolution of the acute episode. Preventive therapy with 3g of thiabendazole once a week was then prescribed, and repeated fecal examinations were negative for larvae. Following discontinuation of treatment, however, the patient again had a positive fecal examination for Strongyloides stercoralis larvae, even though reinfection was considered to be very unlikely. The patient was retreated with a shorter course of therapy and once per week preventive therapy was reintroduced. After four months of follow-up, repeated fecal examinations were negative. When the treatment was changed to thiabendazole given once every two weeks, however, pulmonary Strongyloides stercoralis recurred. Subsequently, because of intolerance to thiabendazole, the patient was treated with cambendazole. The patient died three months later due to Pseudomonas aeruginosa pneumonia. Prolonged therapy for Strongyloides stercoralis infection may be necessary. Although further evaluation is needed, 3g of thiabendazole once a week may be adequate for this purpose. Cambendazole may be a useful alternative for disseminated Strongyloides stercoralis.