This compassionate-use study examined the efficacy of foscarnet in patients with AIDS and cytomegalovirus (CMV) gastrointestinal disease who had failed ganciclovir induction. Nineteen male homosexuals with AIDS and biopsy-proven CMV gastrointestinal disease who had twice failed standard ganciclovir induction (defined as progression of clinical CMV disease) were studied. Foscarnet 60 mg/kg every 8 h was administered intravenously for 14 days, then maintenance was utilized at 90 or 120 mg/kg every day with 1 L normal saline daily. Endpoints included endoscopic appearance, blinded histopathologic analysis of biopsies for CMV inclusions, and changes in symptoms by 50% from baseline. Patients were evaluated before and 2-3 wk after foscarnet. Histopathologic improvement was seen in 67%, whereas 74% improved clinically after a median duration of 7.5 days (1-12). Among the nine with esophageal disease, six patients (68%) had a clinical response and six of eight (75%) had a pathologic response. Among the 10 with colonic disease, eight patients (80%) had a clinical response and six (60%) had a pathologic response. Reversible elevations in creatinine were seen in two of 17 (12%). Three patients with esophageal disease developed strictures late in therapy requiring dilation. Median survival after foscarnet induction was 5.0 months. Foscarnet appears to induce remission of CMV gastrointestinal disease in 67% of patients when ganciclovir induction has failed. Reversible nephrotoxicity occurred in 12%. Strictures may be a late complication of CMV esophagitis.