Upper gastrointestinal endoscopy was performed for the evaluation of infectious esophagitis in 19 consecutive subjects evaluated prospectively before orthotopic liver transplantation (OLTx), in a separate group of 27 subjects post-OLTx, and in 21 subjects following orthotopic renal transplantation (ORTx). None of the pre-OLTx patients had evidence of infectious esophagitis, whereas 11% of the post-OLTx and 24% of the post-ORTx patients had esophageal infections. Candida esophagitis was found only in the post-ORTx patients, whereas cytomegalovirus and herpes simplex viral esophagitis were found in both the post-ORTx and post-OLTx patients. Dysphagia was associated with evidence of herpes simplex virus infection (P less than 0.001) and epigastric pain was associated with Candida infection (P less than 0.001). No association between the administration of prednisone or the blood level of cyclosporine A and esophagitis was found. Finally, the use of standard low-dose mycostatin prophylaxis was not effective for prevention of Candida esophagitis. Nonetheless the use of higher doses of mycostatin was therapeutic.