This report presents the results of a double blind randomized study comprising 50 patients with epithelial herpes simplex keratitis. Twenty-five patients received 3% acyclovir ophthalmic ointment, the other 25 patients 2% trifluorothymidine (TFT) ophthalmic ointment. The mean duration of treatment in the 2 study groups before healing of the epithelial ulceration was obtained was 6.7 days and 5.9 days, respectively (no statistically significant difference). Two patient (8%) in the acyclovir group and 1 patient (4%) in the TFT group failed to heal within 14 days of treatment. No clinically significant adverse effects were recorded.