The densities of beta-1 and beta-2-adrenergic receptors in normal and reeler mice brains were compared using in vitro autoradiography. For the most part, the regional distribution of the beta-receptor subtypes in mouse brain was similar to that of rat [Rainbow et al. (1984) Proc. natn. Acad. Sci. U.S.A. 81, 1585-1589]. The most striking differences in beta-adrenergic receptor localization between the mouse and rat brain were in the superficial layer of the superior colliculus and the bed nucleus of stria terminalis. The superficial layer of the mouse superior colliculus had high densities of beta-1 receptors and much lower densities of beta-2 receptors, while the superficial layer of the rat superior colliculus had moderately high densities of beta-2 and lower densities of beta-1 receptors. The mouse bed nucleus of stria terminalis had greater densities of beta-1 receptors than beta-2 receptors. This structure in the rat possessed roughly equivalent densities of beta-1 and beta-2 receptors. In general, the distributional pattern of beta-1 and beta-2 receptors in the reeler mouse brain matched that of the normal mouse brain. In regions which neuronal malpositioning had been reported, such as the cerebral cortex, hippocampus, and cerebellum, beta-1 and beta-2 receptors were still present in proportions similar to normal mice; however, the pattern of beta-receptors within each of these regions was altered. The beta-receptor subtypes in these structures showed an abnormal radial distribution similar to the abnormal radial positioning of neurons in these structures.