Recombinant alpha-2 interferon (IFN)--Roferon--100,000 IU/ml was intralesionally administered in 8 cases of squamous cell carcinoma (SCC) three times a week during 4-6 weeks in inoculations of 1 ml each. The therapeutic effect was scored as major--more than 60% reduction of the tumor size, moderate--30-60% reduction of the tumor mass and, nonreactive--less than 30% reduction of the tumor size. Three cases showed a major reduction, three showed a moderate reduction and two patients showed no reduction of the tumor volume. Histopathological examination of the surgically removed tumors after completion of the Roferon administration confirmed the clinical diagnosis of squamous cell carcinoma and revealed that an intense leukocyte, mainly lymphocytes, infiltration can be observed along with necrotic centers, progressively surrounding and reducing in size the tumor islets, thus proving an intense activation of the immune effector reactions against tumor cells.