New antiviral compounds are being tested constantly and may be of considerable value with increasing availability. More than 200 analogues of purines and pyrimidines have been found to inhibit DNA and RNA viruses. Adenine arabinoside is most effective against disseminated herpes simplex virus and disseminated herpes zoster. Idoxuridine is useful in treatment of herpetic keratitis. Interferon still is in the experimental stage, and, because of its short half-life and high cost, it probably will not be released in the near future. Amantadine appears to be useful in prevention of A2 influenza, but its value against swine flu has not been established. Methisazone is effective in prevention of smallpox and in the treatment of complications of vaccinia.