Following evaluation studies, patients receive at least 10 days of intravenous (IV) therapy with acyclovir. During this therapy, patients have two serum concentration levels of acyclovir drawn to make sure there are adequate levels of medication in their blood. If skin lesions do not heal after a total of 10 days of therapy with acyclovir, lesions are swabbed for viral culture to test the susceptibility of the virus to therapy with acyclovir, foscarnet, and vidarabine. If the test confirms that the herpes lesions are resistant to acyclovir, patients may choose to participate in the next phase of the study. Following additional evaluation studies, patients are randomized to one of two groups, each of which receives 10-21 days of IV treatment with one of the two alternative medications, foscarnet or vidarabine. Foscarnet is given by IV infusion every 8 hours, and each infusion lasts 1 hour. Vidarabine is given by IV infusion once a day, and each infusion lasts 12 hours. While receiving therapy with either foscarnet or vidarabine, blood tests are done every 3 days for routine lab tests and once a week to determine foscarnet or vidarabine blood levels. Skin lesions are cultured for herpes virus every 5 days. At the end of 10 days of therapy, improvement is evaluated, and the patients can continue to receive therapy if indicated. There is a provision for cross-over treatment if patients show a poor response.