A system has been developed for monitoring motor patterns both in small animals and in semi-intact preparations. Using a video recording system, the optical image of the selected object is projected onto a TV monitor to which is attached a pair of photosensitive resistors or diodes. The signals from the photosensor are amplified, filtered prior to being recorded, or stored using commercially available data capture systems. Use of the paired photosensitive elements allows us to avoid changes in background illumination, using a differential amplification function, during different patterns of activity of monitored organs or animals and also allows us to record activity from several different organs or systems simultaneously. The simplicity of the system enables us to perform simultaneous monitoring of both effector movements and neuronal activity via multi-channel microelectrode recordings. We have tested this system using semi-intact preparations of the freshwater pulmonate snail, Lymnaea stagnalis. Examples of different types of recordings are presented.