In a prospective non-randomized study 21 patients with lower lip squamous cell carcinoma were treated with human natural leukocyte interferon (HNLI). The response rate was measured by a size reduction of more than 25% and was 81%. A complete response rate was considered to be a cure according to histopathological and clinical findings and was 48%. The response rate of six lower lip squamous cell carcinoma cases treated with recombinant interferon alpha 2c was 67% and the complete response rate was 17%. Three patients with basal cell carcinoma of the upper lip were also treated with HNLI. All three patients were cured, as determined by histopathological and clinical findings. These findings indicate that interferon can be a useful alternative therapy for lip carcinoma either with or without surgery.