Ara A is a relatively insoluble compound that has topical antiviral activity and potency identical to those of IDU. Patients allergic or resistant to one may successfully use the other, and they represent valuable alternatives. Intravenously, Ara A has been shown in our double-blind studies to be effective against herpetic iritis and deep stromal disease, whereas no topical agent has been shown to be of use in man in treating these problems. Its intravenous use was not associated with significant toxicity.