AbstractBifurcation of the axon of unipolar neurons in the dorsal root ganglion of the cat has been studied by light and electron microscopy.Osmic acid, Golgi and silver preparations have revealed two types of bifurcation: (1) of myelinated fibers characterized by constriction at the nodal region with peripheral and central branches of equal diameter; (2) of small fibers characterized by a broad triangular expansion at the junctional region with a much thicker peripheral as compared to the central branch. These differences in bifurcation of unmyelinated and myelinated axons can be related to the velocity of conduction in the peripheral nerve and dorsal roots.The ultrastructure of the nodal region at the bifurcation resembles the node of Ranvier of a peripheral nerve fiber. The node of Ranvier at the bifurcation consists of three cells of Schwann and adjacent cells are closely apposed and interdigitated.Neurofilaments and microtubules are prominent structures within the axoplasm at the nodal regions. They group into two streams as the unipolar process bifurcates, entering the peripheral and central branch respectively. At the junctional region within the axoplasm, numerous mitochondria and scattered multivesicular bodies are always observed.