Distribution of H-2 antigens in cryostat sections of mouse normal tissues has been studied by immunofluorescence. A combination of inbred strains allowing genetic control of the findings was used. Because of considerable nonspecific staining encountered in sections of solid normal tissues treated with isoantisera, it has been necessary to use a chromatographically purified conjugate to obtain reliable results. Antigenic material has been detected in spleen, liver, pancreas, and brain of C3H, CBA, and C57BL mice. The localization of specific fluorescence for a given tissue was similar in the three inbred strains.