Patch-clamp recordings were made from ON starburst cholinergic amacrine cells with somas located in the ganglion cell layer of an isolated, dark-adapted rabbit retina preparation. Light responses were analysed and cell identify was confirmed anatomically. The centre light response had a linear current-voltage relation with a reversal potential close to 0 mV. The receptive field size was similar to the dendritic field size. Cholinergic amacrine cells displayed significant surround inhibition. The receptive field profile consisted of a central excitatory region flanked by an inhibitory surround. The surround attenuated the central response to 36% of the maximum. The surround was probably mediated by a combination of presynaptic and postsynaptic inhibition. Starburst amacrine cells did not display action potentials and the presence of a large, voltage-dependent outward current limited depolarizing responses to a maximum potential of about -40 mV. Light responses were completely suppressed during application of 100 microM D,L-2-amino-4-phosphonobutyric acid (APB), consistent with activation exclusively through rod bipolar cells (on) and ON-cone bipolar cells. In darkness the cells displayed a tonic inward current that could be blocked by 100 microM APB and 2 microM CNQX.