Horizontal cells of salamander retina were intracellularly injected with horseradish peroxidase, and the histochemical reaction used to identify their processes and contacts at the level of the electron microscope. Horizontal cell bodies are linked to their axonal terminals by a very fine axon. Both segments make ribbon and distal junctions with rods and cones. Bipolar cells are postsynaptic to both axon terminals and cell bodies, but only the latter are in turn postsynaptic to bipolar cells. This bipolar cell input depolarizes the cell bodies when the surround is illuminated, and explains why their responses differ from those recorded at the axon terminals. BIBLIOGRAPHIC REFERENCE: Lasansky, A.: Interactions between horizontal cells of the salamander retina. Invest. Ophthal. 15: 909-916, 1976.