The samples of mononuclear cells (PBMC) isolated from the blood of healthy donors (HD) and from the blood of patients with chronic virus B hepatitis (HV) were exposed to 1300 MHz pulse modulated microwaves at 330 pps with 5 µs pulse width, or left without irradiation. The specific absorption rate (SAR) was measured and the value of SAR = 0.18 W/kg was recorded. The microcultures of PBMC were subsequently set up to determine several parameters characterizing the T cell immunocompetence and monocyte immunogenic activity, including: proliferative response to mitogens (PHA, Con A), saturation of IL-2 receptors, T cell suppressive activity (SAT index), monocyte immunogenic activity (LM index) and production of chosen cytokines. The same absorbed dose of 1 mW/cm² reduced response to PHA in HD cultures and significantly increased this response in HV cultures, increased values of SAT and saturation of IL-2 receptors in the both HD and HV cultures and significantly increased production of interferon gamma (IFNγ) and production of tumor necrosis factor alpha (TNFα) in the HV cultures but not in the HD cultures. The results suggest that microwave irradiation (1300 MHz, pulse modulated) may exert distinct immunotropic influence and may enhance the effector immune response in patients with chornic virus B hepatitis, including considerable stimulation of the production IFNγ by immune cells.