Contralateral-control methods can be applied to psychophysiology and in particular to the study of visual memory. Visual memory possesses some degree of hemispheric organization, so that visual memory traces for laterally presented stimuli are stronger or more durable in the hemisphere contralateral to the hemifield where the stimuli were first presented. I first introduce the concept of hemispheric organization of function. Then I discuss how hemispheric organization can be exploited for obtaining information about the time course and brain localization of psychological processes, using a contralateral-control method. Behavioral and event-related brain potential data support the hemispheric organization view of visual memory, and the contralateral-control method, in conjunction with the recording of the event-related optical signal, can be used to reveal the existence of memory-driven processes in early stations of the visual system.