The studies were carried out on the claustrum of 8 adult rabbits. Four types of neurons were distinguished: 1. Multipolar neurons, which have dendritic trunks either with conus (multipolar polygonal perikarya) or without conus (multipolar rounded perikarya). Both subdivisions of the multipolar neurons have 3-6 dendritic trunks. Only some branches of these trunks have spines. An axon emerges mainly from the cell body, rarely from the initial part of the dendritic trunk. 2. Bipolar neurons with fusiform or rounded perikarya; they have two dendrites covered with spines. An axon originates directly from the cell body or from one of the dendritic trunks. 3. Triangular neurons, which have three dendritic branches with spines. An axon emerges directly from the soma, often near the primary dendritic trunk. 4. Pear-shaped neurons with one or two dendritic trunks arise from one pole of the cell body and with an axon that originates from the opposite side of the perikaryon. The dendrites are covered with spines.