An antibody to microtubule-associated protein 2 (MAP2) has been used to examine the arrangements of neurons in striate cortex of the cat. It is found that the apical dendrites of medium-sized and large pyramidal cells in layer V group together to form clusters that have a center-to-center spacing of about 56 μm. As these clusters ascend, the apical dendrites of pyramidal cells in layer ll/lll are added to them. The thinner apical dendrites of the smaller pyramidal cells in layer VIa also form groups that are referred to as bundles. These bundles ascend into layer IV independent of the clusters, and their arrangement suggests that the bundles are formed so that the apical dendrites of the layer VIa pyramids can pass between the groups of cell bodies of the layer V neurons.