A 36-year-old man with a 5-year history of untreated human immunodeficiency virus (HIV) infection had odynophagia for 14 days. Fifteen days earlier, he had begun taking trimethoprim-sulphamethoxazole and combination antiretroviral therapy that included lamivudine, zidovudine, and nelfinavir. He had no history of opportunistic infection. The CD4 lymphocyte count was 67/μL and HIV-RNA level was 359,396 copies/mL. Esophagogastroduodenoscopy revealed a large, well-circumscribed esophageal ulceration 31 cm from the incisors. Histopathologic examination of esophageal biopsy specimens showed cytopathic changes diagnostic of cytomegalovirus (CMV). In situ DNA hybridization was positive for CMV. While combination antiretroviral therapy was continued, the esophageal symptoms resolved within 4 days of endoscopy without specific therapy for CMV. Follow-up endoscopy 4 weeks later revealed a normal-appearing esophagus, and the patient has remained symptom-free for 10 months.