9-(1,3-dihydroxy-2-propoxymethyl) guanine (ganciclovir) was used to treat 41 patients (median age, 37 years) with the acquired immunodeficiency syndrome and cytomegalovirus gastrointestinal infection. Sites of infection were the colon in 31, the esophagus in 5, the rectum in 4, and the small bowel in 1. Patients received ganciclovir, 5 mg/kg body weight, intravenously every 12 hours for 14 days. Clinical improvement was seen in 30 patients and virologic response in 32. Mainly hematologic toxicity occurred: moderate leukopenia (1000 to 1900/mm3) was seen in 7 patients and severe (less than 1000/mm3) in 1, and moderate neutropenia (500 to 1000/mm3) in 5 and severe (less than 500/mm3) in 1. A cutaneous rash developed in 2 patients. Median overall survival was 16 weeks (range, 2 to 56). Cytomegalovirus recurred in 13 patients; median time to recurrence was 9 weeks from the start of treatment. Ganciclovir may be effective in treating cytomegalovirus gastrointestinal disease in patients with the acquired immunodeficiency syndrome.