Light exposure activates dopamine (DA)-releasing neurons in the retina. Previous studies have employed indirect means (i.e. accumulation of DA metabolites in vivo4.11, or [3H]DA release from preloaded retina in vitro2) to estimate light-stimulated retinal DA release. We describe a new technique, based on superfusion of retinal pieces in vitro, which allows direct measurement of endogenous DA release. Dark-adapted pieces of retina from male albino rabbits were individually superfused in vitro with a physiologic buffer containing nomifensine (30 microM) (a DA reuptake blocker), and exposed to steady white light (300 microW/cm2) for 15 min. Retinal DA release into the superfusate was significantly greater (60%) during photic stimulation than during dark-exposure.