It is known that the sorbitol pathway, in which aldose reductase (AR) is the first enzyme, causes various diabetic complications. Aldose reductase inhibitors play an important role in the control of the sorbitol pathway and in the prevention of some diabetic complications. In this study, we developed a new spectrophotometric method for determination of erythrocyte aldose reductase activity. The average coefficent of variations within and between assays was 8.9 % and 10.15 %, respectively. Analytical recovery was 94.4 %. This method requires much simpler equipment and is cheaper than other methods. It may be used routinely for the determination of erythrocyte aldose reductase activity that may provide useful information for the regulation of the dose of aldose reductase inhibitors used for the prevention as well as treatment of diabetic complications.