The study presents data on the effects of low doses of gamma radiation on the immunological status of sheep of the Prekos breed in single and two-times exposures with an interval of 60 days. The level of immunoglobulin IgM was increased after a single gamma-irradiation in doses 0,65 · 10–2 C/kg (25 R), 1,29 · 10–2 C/kg (50 R), 2,58 · 10–2 C/kg (100R), 5–15 days after radiation exposure by 10–15 %, the concentration of antibodies of classes Ig G and Ig A were decreased in the same period by 15–30 %. The study indicated a dose dependent increase in the level of circulating immune complexes in serum by 5–20 % on the 5th day after radiation exposure. It is found that low doses of ionizing radiation at two fold exposure radiation in the range of 0,65 · 10–2 C/kg + 1,95 · 10–2 C/kg (25 R + 75 R) and 1,29 · 10–2 C/kg + 1,29 · 10–2 C/kg (50 R + 50 R) stimulate the immunobiological reactivity of the organism of sheep to a greater degree than single exposure. It was noted a statistically significant, consistent increase in the level of all major immunoglobulin classes in the serum: Ig M – 5–10 days after exposure – by 25–30 %, Ig G – 10–15 days after exposure – by 15–20 %, Ig A – 10–30 days after exposure – 25–30 %. The content of circulating immune complexes was decreased by 10–20 % compared to those of intact animals. These results indicate the expression in the irradiated organism-specific antigenic sti-mulation, which appears specific immune response according to primary (at the first radiation exposure) and seconddary (after repeated radiation exposure) immune response.