Illumination of the receptive field surround reduces a retinal ganglion cell's sensitivity to center illumination. The steady, antagonistic receptive field surround of retinal ganglion cells is classically attributed to the signaling of horizontal cells in the outer plexiform layer (OPL). However, amacrine cell signaling in the inner plexiform layer (IPL) also contributes to the ganglion cell steady receptive field surround. We examined the contributions of these two forms of presynaptic lateral inhibition to ganglion cell light sensitivity by measuring the effects of surround illumination on EPSCs evoked by center illumination. GABAC receptor antagonists reduced inhibition attributed to dim surround illumination, suggesting that this inhibition was mediated by signaling to bipolar cell axon terminals. Brighter surround illumination reduced the ganglion cell light sensitivity further. The bright surround effects on the EPSCs were insensitive to GABA receptor blockers. Perturbing outer retinal signaling with either carbenoxolone or cobalt blocked the effects of the bright surround illumination, but not the effects of dim surround illumination. We found that the light sensitivities of presynaptic, inhibitory pathways in IPL and OPL were different. GABAC receptor blockers reduced dim surround inhibition, suggesting it was mediated in the IPL. By contrast, carbenoxolone and cobalt reduced bright surround, suggesting it was mediated by horizontal cells in the OPL. Direct amacrine cell input to ganglion cells, mediated by GABAA receptors, comprised another surround pathway that was most effectively activated by bright illumination. Our results suggest that surround activation of lateral pathways in the IPL and OPL differently modulate the ganglion cell's sensitivity to center illumination.