In the pig eye, oxygen and glucose consumption in the outer retina are reduced in light compared to the consumption in the dark and most of the glucose consumed is metabolized to lactate both in light and in the dark. In the present study, in order to characterize the metabolism of glucose in the inner retina. Blood was collected from an artery and from a plexus on the optic nerve draining blood from the retina. Arteriovenous concentration differences for glucose, lactate and oxygen were determined. Observations were made in dark-adapted eyes and then after light adaptation. The consumption of oxygen and glucose and the lactate formation in the inner retina were calculated on the basis of these observations and recent data for retinal blood flow. In dark-adapted eyes, approx. 69% of the glucose was oxidized and approx. 20% was used in lactate formation. After 5-10 min of exposure to constant light, the levels of oxygen consumption and lactate formation were no different from those in darkness. The results indicate that lactate formation is a normal property of the pig inner retina, but that it is much less pronounced than in the outer part. The metabolism of the inner retina in constant light is similar to that in darkness. A comparison with data for the outer retina indicates that oxygen consumption in the inner retina in constant light is approx. 47% of that in the whole retina, while for glucose consumption and lactate production, the corresponding figures are approx. 12 and 8%, respectively.