This open label study evaluated the effect of nine intralesional injections of two different doses of interferon gamma on basal cell carcinomas in 29 patients. One group of 15 patients received interferon gamma, 0.01 mg (20,000 IU), intralesionally three times a week for 3 weeks. Fourteen patients received interferon gamma, 0.05 mg (100,000 IU), intralesionally in the same dosage schedule. Excisional biopsy specimens 12 weeks after therapy showed no evidence of tumor remaining in 7 of 14 patients (50%) treated with the higher dose of interferon gamma, whereas only 1 of 15 patients (7%) treated with low-dose interferon gamma was cured according to histologic criteria (p = 0.025). Seventy-six percent of patients reported at least one adverse reaction, but most were considered mild by the patient and the investigator. © 1990, American Academy of Dermatology, Inc.. All rights reserved.