The present studies were carried out in order to assess the protective effects of selenium against cadmium toxicity in pregnant hamsters. On the 8th day of gestation the females were dosed subcutaneously either with cadmium or with cadmium and selenium in the following doses (mg per kilogram of body weight): 0, 1 Cd, 1 Cd + 1 Se, 2 Cd, 2 Cd + 2 Se. In groups treated with cadmium: decreased litter size, increased postimplantation losses, reduced foetal weight, elevated percentage of resorptions and increased incidence of malformations were noted. Injection of Cd and Se resulted in significantly lower embryo- and foetotoxic indices. Selenium also reduced Cd concentration in maternal tissues but not in the placenta nor in the foetuses.