Infection with Strongyloides stercoralis, the most common intestinal parasite at our hospital, was encountered in 56 patients over a 3-yr period. The majority of the patients were male adults over 50 years old who had a chronic debilitating associated illness; about half the patients were immunocompromised. Strongyloidiasis was usually a chronic relapsing illness of mild to moderate severity characterized by gastrointestinal complaints (diarrhea, pain, tenderness, nausea, vomiting) and peripheral eosinophilia. Hypoalbuminemia also occurred. Stool examination for larvae was an effective method of diagnosing the parasite, and treatment with thiabendazole was usually successful. The frequent occurrence of S. stercoralis in geriatric patients with other medical problems and the delays in making the diagnosis suggest that the clinical spectrum of strongyloidiasis is greater than generally appreciated by the medical profession. Increased awareness of S. stercoralis is important to prevent the hyperinfection syndrome, which was estimated to occur in 1.5-2.5% of our patients.