Using the immunocytochemical method, the localization of calretinin-positive cells was studied in the frontal sections of anterior portion of the mouse cerebral hemispheres. The population of cells with a characteristic structure, that was not described previously, was detected in the area of anterior horns of lateral brain ventricles. These cells have small (8-10 μm) rounded perikarya which gave rise to 1 or, rarely, 2 nodose processes covered with widely spaced, polymorphous spines (PS) and irregular thickenings. Primary, relatively thick, processes divide to produce thinner processes that also formed thickenings and spines of different dimensions and structure. Calretinin-positive cells with PS (CR+PS) cells are located in the white subcortical matter, layer VI, more rarely in layer V of the frontal area of dorsome-dial cortex close to the cingulum. CR+PS cells were also present in rostro-dorsal part of the caudate nucleus-putamen complex, anterior olfactory nucleus, subependymal layer of the dorso-lateral angle of the lateral ventricle, and, less frequently, near its dorsal wall. In contrast to mouse brain, CR+PS cells were not found in the brain of other animals (rats, rabbits, cats).Within CR+PS cells, no co-localization of calretinin with GABA and other neuronal or glial markers was found. It is suggested that the cells described represent previously unknown, presumably non-neuronal type of the mouse forebrain.