This work was designed to analyze the possible dose dependent effects of cadmium on the blood lymphocyte subset distribution and if these effects are related to circulating cadmium concentration. For that purpose, adult male rats were exposed for one month to 0, 5, 10, 25, 50 or 100 ppm of cadmium chloride (CdCl2) in the drinking water. B lymphocytes decreased in peripheral blood with the doses of 5 and 10 ppm of CdCl2. From the dose of 25 ppm on, B cells increased. T lymphocytes were increased with the doses of 25, 50 and 100 ppm of CdCl2. The lower doses of the metal induced opposite effects. CD4+ and CD8+ cells decreased with the doses of 5 and 10 ppm whereas they were increased with the dose of 25 ppm of CdCl2 on. From the dose of 10 ppm on, cadmium concentration was increased. The results on the distribution of blood lymphocyte subsets suggest that cadmium inhibits the humoral and cellular immune response with the lower doses of the metal used, and opposite effects were detected with the higher doses, the effect not being dependent on the circulating cadmium.