Patients must have AIDS as defined by the CDC or be immunocompromised (transplant patients; other hematologic malignancies with recognized cell-mediated immune deficiency). Patients must also have herpes simplex virus (HSV) infection documented by culture and in vitro resistance to acyclovir by standard laboratory susceptibility or suspected resistance to acyclovir after an acyclovir treatment failure in which acyclovir was administered for at least 2 weeks intravenously at doses of 30 mg/kg/day (or a comparative dose adjusted for renal insufficiency). In vitro susceptibility data must be pending in the latter case. Patients must be able to give informed consent. Patients < 18 years of age may participate with the consent of parent, guardian, or person with power of attorney, or through the provisions of state laws regarding emancipated minors. Patients must have expected survival of at least 6 months.