[en] As ¹⁹²Ir is increasingly being used in solid form and can enter into the organism during the production of soluble compounds, the knowledge of its distribution in the organism and its excretion is important to estimate a possible radiation damage. Investigations were thus carried out on the whole body and organ radioactivity as well as the measuring of the excretion of ¹⁹²Ir in urine and feces of 155 male Wistar rats after intravenous injection of 1.4 μCi ¹⁹²Ir in the form of ammonium hexachloroiridate (IV). The radioactivity in the whole body decreases a day after injecting the ¹⁹²Ir to about a fifth of the initial radioactivity. From the 14th day of investigation on, the effective half-life of the whole body radioactivity with two test series, is 26.2 days, with a further series, 26.1 days; the accumulated excretion in the urine and feces increases accordingly. Two hours after injecting the ¹⁹²Ir, the radioactivity is at its highest in the skeletal muscles, the whole blood, in the total skeleton as well as in the liver and kidneys. On the 40th day of investigation, the highest ¹⁹²Ir accumulation was found in the whole skeletal muscles and in the whole skeleton as well as in the kidneys, liver, small intestine, whole blood, spleen, lungs and testicles. The effective half-life in epididymis, skeletal muscles, kidneys, heart, liver, lungs, testes, suprarenal glands and whole blood is lower than in the other organs investigated. (orig./LH)