The effects on retinal ganglion cells of iontophoretically applied glycine, taurine and strychnine were studied in the optically intact eye of the cat. Glycine and taurine suppressed the light-evoked discharge of all on-centre and off-centre brisk ganglion cells, regardless of the visual stimulus used. Strychnine blocked the action of externally applied glycine and taurine. The light-evoked response of all ganglion cells was raised by strychnine. The tonic discharge of the light response was suppressed or raised by the drugs more than the phasic response. A population of amacrine cells, which was heavily labelled by [3H]glycine, did not take up [3H]taurine. [3H]taurine was only weakly accumulated by inner nuclear layer neurones and was predominantly located in the outer retina.