BVDU [(E)-5-(2-bromovinyl)-2'-deoxyuridine] has a potent and selective activity against herpes simplex (type 1) in both cell culture systems and animal models. The efficacy of topical BVDU treatment (0.1% eye drops) has been evaluated in 37 patients with different forms of herpes simplex keratitis. Of these patients, 35 were followed for 2-9 months (average 6.5 months). Most of the patients had first been treated with topical IDU (idoxuridine) or ara-A (adenine arabinoside), albeit unsuccessfully, before BVDU treatment was started. Upon BVDU treatment, dendritic corneal ulcers healed in 7.8 days (on average) and the geographic corneal ulcers in 10.8 days. BVDU also exerted a pronounced healing effect on stromal keratitis, whether it was used alone or in combination with topical corticosteroids. No early recurrences were observed. Late recurrences were seen in four patients who again responded quickly to BVDU treatment. No toxic side effects, whether local or systemic, were noted in any of the patients treated with BVDU. These results establish the efficacy of BVDU in the local treatment of herpetic keratitis in man.