Immunoregulatory T-lymphocytes (T mu- and T gamma-lymphocytes) and circulating immune complexes were studied in inoperable patients with the stomach carcinoma of stages III-IV. It is established that the absolute number of T-lymphocytes, mainly of T-helpers/inductors increases after the administration of indomethacin and 5-fluorouracil with indomethacin. The T mu/T gamma-lymphocyte ratio increases and approaches the control values. The level of the circulating immune complexes tends to be normalized. The main effect of indomethacin is determined by the effect of T-lymphocytes on immunoregulatory subpopulations.