Spike trains were recorded simultaneously from pairs of auditory nerve fibres in anesthetized cats. Tests for correlation between spike trains were developed for spontaneous activity and for discharge patterns resulting from single-tone stimuli. The application of these tests to the recordings indicates that the responses of auditory nerve fibers to a tone and to silence can be described as statistically independent point processes. This result implies that the initiation of spikes in these fibers is governed by localized processes specific for each fiber.