The effect of age on vitamin B6 metabolism was studied in 617 community-dwelling subjects, ages 18 to 90. These are, for the most part, clinically healthy, educated men whose intake of nutrients is not limited by economic factors. Plasma pyridoxal phosphate (PLP) was used as the primary criterion of vitamin B6 status. About one-third of the subjects were taking supplementary vitamins on their own initiative. The amount of pyridoxine-HCl varied from 0.1 to 105 mg/day. The average plasma PLP of the men not taking a supplement (N = 414) was 12.3 +/-0.3 ng/ml, with 25% of the values below 7.5 ng/ml and 7% below 5 ng/ml. There was a statistically significant decrease in plasma PLP with age of 0.9 ng/ml per decade. For those taking a supplement, the average plasma PLP was 20.5 +/- 1.0 ng/ml, with only 8% of the values below 7.5 ng/ml and none below 5 ng/ml. Glutamic-oxaloacetic transaminase activity in plasma (PGOT) and erythrocytes (EGOT) was determined on all subjects. The ratio of EGOT with in vitro stimulation by PLP to EGOT actual (alpha-EGOT) was also studied. These studies provide the most extensive normative data on vitamin B6 status available on men in the adult years of life.