A double-blind comparative trial of acyclovir (ACV) and adenine arabinoside (ARA-A) in combination with dilute betamethasone was carried out in 30 patients with herpetic disciform keratitis. Of those receiving ACV and betamethasone, 86.7% healed in a mean time of 22.5 days, while 76.9% of those receiving the Ara-A combination healed in a mean time of 26.7 days. There was no statistical difference between the two treatment groups for efficacy parameters. However, the proportion of patients developing superficial punctate keratopathy (SPK) was significantly greater in the Ara-A treatment group.