[en] The dynamic of the whole body retention in rats after iv ⁷⁵Se-methionine was determined b y whole body counting. The retention was well described by a three-component equation: R(t) = 24.06 e^-0.679t + 41.24e^-0.042 + 15.41 e^-0.005t wherein the t_1/2 were T₁ 1.0d, T₂ = 16.4 d, T₃ =132 d. The radioactivities in urine revealed 2 components with t_1/2 = 0.6 and 9.8 d respectively. Biological t_1/2 5.2 d in fecal excretion for the fast component and 13.2 d for the long term component. The autoradiographic study indicated that after iv ⁷⁵Se-methionine in rats the radioactivity accumulated chiefly in pancreas, and then in liver, skeleton and thyroid gland, only a trace amount of it was found in hair. A method was studied for rapid preparation of autoradiographs for tissue slices by impregnation of nuclear emulsion with liquid scintillators PPO and POPOP. Mixing liquid scintillators, especially a hydrophilic dioxane solvent, with emulsion allowed also rapid autoradiographic grain production. The tissue distribution of ⁷⁵Se-methionine by fluorescence-sensitized autoradiography was observed after iv ⁷⁵Se-methionine. The number of autoradiographic grains/10 μm² was increased with the scintillator by 4-10 times. The silver grains in the autoradiograms were distributed high in the pancreatic acini and the islets, and then in liver cells, bone marrow and epithelial cells of thyroid gland