Using antibodies against calcium-binding proteins immunocytochemistry revealed quantitative staining of horizontal cells in whole mount preparations. In cat both A- and B-type horizontal cells, and in monkey probable H1- and H2-horizontal cells were labelled with antibodies against parvalbumin. In rabbit and ox two types of horizontal cell were labelled with antibodies against calcium-binding protein (CaBP-28K). In ox retina processes of horizontal cells were observed descending into the inner plexiform layer (IPL).