The proposed clinical trial will evaluate the efficacy of topically-applied thalidomide as a treatment for painful oral lesions in HIV-infected patients. Limited data suggest that this drug may be effective when given systemically, but is accompanied by a high incidence of side effects. Administration of the drug topically onto the lesion should result in high local concentrations within the lesion thereby suppressing tumor necrosis factor which is thought to be related to the size and severity of the lesion. Subjects will be randomly allocated to one of three possible groups: systemic administration of thalidomide, topical administration of thalidomide, and placebo. The dose of thalidomide will be determined in a dose escalation pilot study prior to the main study. Healing, pain, and the incidence of side effects will be assessed at baseline and weekly for up to eight weeks. Successful demonstration of an enhanced therapeutic effect or reduced toxicity may provide a basis for the development of novel routes of administration and drugs for the treatment of painful oral lesions associated with HIV infection and other diseases.