A morphological analysis of some structures of the archicortex and neocortex was performed in the Acomys cahirinus (spiny mouse), the only precocial murid. The data obtained indicate that the spiny mouse brain is an interesting case of a largely developed hippocampus with respect to the neocortex when compared to the brains of the mouse and rat. The precocious pups of the spiny mouse present the peculiarity among Murids of an early olfactory imprinting.