Retention, dynamics of 75Se and 65Zn distribution, and elimination were studied in rats after separate or joint single doses of these metals. White female Wistar rats were divided into four groups (fifteen rats each). Group I received Na2(75)SeO3 (0.1 mg Se/kg i.g.), group II received Na2(75)SeO3 + ZnCl2 (5 mg Zn/kg s.c.), group III received 65ZnCl2, and group IV received 65ZnCl2 + Na2SeO3. The zinc and selenium contents in the tissues were estimated during 120 h after administration; excretion in urine and feces of animals was determined throughout the experiment. Combined administration of zinc and selenium resulted in an enhanced selenium retention in the brain, spleen, kidneys, blood, lungs, and heart. A selenium-induced increase in the concentration of zinc was noted in the bowels, blood, liver, kidneys, spleen, brain, and lungs. The effects of the zinc/selenium interaction were visible especially in the lowered level of excretion of these elements. Zinc induced a decrease in the excretion of selenium in urine, with no concomitant changes in the excretion in feces. However, a visible decrease in the excretion of zinc in the feces was observed in the presence of selenium. The present results indicate an occurrence of clear-cut interaction effects between zinc and selenium administered simultaneously in the rat.