The metabolism of the retinae from alloxan-diabetic rabbits has been compared with that of the retinae of normal rabbits. With glucose substrate, the Qo and QN2G were significantly lower in the alloxan-diabetic than in the normal rabbit retinae. The Qo2 of the normal rabbit retinae was the same with pyruvate as substrate as with glucose. With the retinae from alloxan-diabetic rabbits, the Qo2 with pyruvate as substrate was significantly greater than the Qo2 with glucose as substrate, as well as the Qo2 of the normal rabbit retinae with pyruvate substrate.