The variation in the number of spikes in responses of frog retinal ganglion cells has been investigated with correlation and other statistical measures. The On and Off responses produced by the same light flash are either uncorrelated or weakly negatively correlated with each other when their averages are stationary in time. Early parts of the Off response are highly negatively correlated with late parts. A weaker negative correlation exists between the early versus late parts of the On response. A model for response generation is considered in which the On and Off responses are mediated by independent bipolar cell pathways, each with its own sustained and transient amacrine cell inhibition. © 1983.