Glutamate dehydrogenase was purified from the liver of immature (4-weeks), young (22-weeks) and old (116-weeks) female rats to study the effect of age on this enzyme. From 30 g of liver tissue of each age group, approximately 90-fold purified enzyme was obtained in crystalline form with an average yield of 4% of the original enzyme activity. This 4% enzyme was used extensively for analyzing its age-related properties. The elution profile on a Sephadex G-200 column, molecular weight (53,000 +/- 3,000), ratio of A280/260 (1.8), optimum pH (7.8), optimum temperature (25 degrees C), and Km values for different substrates/coenzymes of the purified enzymes did not show marked age-dependent variations. Similarly, remarkable differences were not observed in the effect of a variety of nucleotides or steroid hormones on the activity of the purified enzymes of the three ages. These findings may suggest that rat liver glutamate dehydrogenase is an unaltered enzyme with advancing age of the animal.