Histochemical studies on the cell density of catecholaminergic (CA-) cells were conducted with flat-mounted preparations of the carp ( Cyprinus carpio) retina. Pretreatment of the fish with intramuscular injection of reserpine (R) completely depleted endogenous CA from the retina. CA-cell fluorescence was accentuated and the number of cells in which a positive reaction was obtained was considerably increased by intraperitoneal injection of l-DOPA (“pDOPA” preparations) or by intravitreal injection of noradrenaline (NA) to reserpinized carps (“R+NA” preparations). The average CA-cell density was 52±6, 84±28 and 104±24 cells/mm 2 in control, “pDOPA” and “R+NA” preparations, respectively. Differences in the spatial density were found to be statistically insignificant among the quartered areas with the optic disk as center, whereas they were significant between the central or intermediate zone and the peripheral zone. The spatial density in control retinas was 43±11, 48±13 and 68±18 cells/mm 2 in the three concentric zones, respectively. The size of CA-cells tended to be smaller where the cell density was higher.