Significant decreases in plasma pyridoxal-5-phosphate (PLP), plasma glutamic-oxaloacetic transaminase (PGOT) and erythrocyte glutamic-oxaloacetic transaminase (EGOT) were found in 29 uremic patients including 14 who had been on hemodialysis an average of 15.8 months. The mean PLP values of the uremic patients (5.39 +/- 0.37 ng/ml) were clearly lower than the values obtained for the normal group (9.30 +/- 0.80 mg/ml). The mean PGOT values of the uremic patients (dialyzed 4.07 +/- 0.29 U/liter, undialyzed 5.31 +/- 0.49 U/liter) were significantly lower than the normal group (6.57 +/- 0.39 U/liter). The mean EGOT value of the uremic patients (325 +/- 17 U/liter) was also lower than normal subjects (416 +/-21 U/liter). Stimulation of the EGOT by exogenous PLP (EGOT index) was less in dialyzed patients (1.60) than normal subjects (1.80) while the undialyzed uremic subjects had a greater than normal stimulation (2.12). All of these results indicate that uremic patients are vitamin B6 deficient and that those undergoing hemodialysis may have decreased amounts of the EGOT apoenzyme.