This study examined the effects of aging and dietary restriction on metabotropic type 1 (met1; high quisqualate affinity) and type 2 (met2; low quisqualate affinity) binding sites for glutamate and the relationship between these binding sites and spatial memory. Quantitative autoradiography was performed on 3-, 10-, and 26-month-old mice. Ten- and 26-month-old mice were fed ad libitum or fed restricted diets. Met1 binding sites were not notably affected by age or diet. Binding to met2 sites was maintained during aging in the ad libitum-fed mice, but there were decreases in binding in the diet-restricted mice as compared to 3-month-old mice. Binding to met1 and met2 sites did not correlate significantly with performance in the Morris water maze. These results suggest that dietary restriction induces a decrease in one or more of the functions associated with met2 binding sites during the aging process.