The study established an immunomodulating effect of preparations of human leukocytic interferon in spontaneous rosette-formation test (E--RFC) and leukocyte adherence inhibition reaction (LAI) which takes place both in healthy donors and patients with cervical carcinoma. In E--RFC test, administration of interferon preparations caused the E-rosette forming cell fraction to increase in donors. A similar but much lower effect was observed in the patient group. The effect of interferon produced by patients leukocytes was low. In LAI test, interferon treatment eliminated tumor antigen-induced inhibition in cases of cell-mediated immunity. However, it failed to materially affect the fraction of adhering cells in cases of negative reaction.