An indirect immunofluorescent test based on globulin preparation from a highly specific antiserum against rat liver DNA polymerase alpha was used to direct the enzyme in sections of various tissues of the rat. The immunofluorescent staining was found in cells of the thymus and the wall of intestine crypt, in sparse cells of the intestinal muscular layer, and in cells of the embryo skin epithelium. In sections of liver the intensity of staining and the number of stained cells increased significantly during regeneration. The immunoglobulins did not interact with the cytoplasm and nuclei of skeletal muscle myotubes, with the epithelial cells at the top of intestinal villi, and with erythrocytes. The intracellular localization of the fluorescence observed was of two general types: 1) staining in the region of the nuclear envelope and/or in the cytoplasm; 2) an additional intranuclear staining. The staining of the first type is characteristic of the cells of intact liver and of leyomyocytes. It was also observed in the proliferating cells of thymus and crypt wall, and in cultured myogenic L6 cells. Cells of the embryo skin epithelium, the satellite cells in the skeletal muscle, and about one half of the regenerating liver cells appeared to have the second type of staining. These data serve an indication of possible histotypical differences in in the intracellular localization of DNA polymerase alpha in proliferating cells. It is proposed that the presence of DNA polymerase in resting cells is in association with their ability to respond to the mitogenic stimulus.