Synchronous firing of spatially separate neurons was studied with multi-electrode recordings in area 17 of the visual cortex of strabismic cats which had developed behaviourally verified amblyopia of the deviated eye. Responses of neurons were evoked with moving light bars or gratings of different spatial frequency. Neurons driven by the normal eye displayed stronger synchronization of their responses than neurons dominated by the amblyopic eye. These interocular differences were highly significant and particularly pronounced for grating stimuli of high spatial frequency. No interocular differences were noted with respect to the amplitudes of responses to the light bars and gratings. These results suggest reduced synchronization of population responses as a neurophysiological correlate of strabismic amblyopia and underline the importance of correlated firing of spatially separate cortical neurons for normal processing of visual information.