An experiment was conducted to evaluate the erythrocyte glutamate-oxaloacetate transaminase activity coefficient (EGOT-Ac) as a biochemical indicator of vitamin B-6 status and to document clinical effects of a B-6 deficiency in mature swine. A 12% crude protein diet, formulated with cornstarch and an isolated soy protein, was analyzed to contain .24 ppm B-6. Sixty-one gilts, initially averaging 111 kg, were individually fed 1.9 kg daily of a diet providing .45, 1.8, or 90 mg B-6/d (treatments (Trt) 1, 2 and 3, respectively). In addition, another group of gilts was fed 90 mg B-6 for the initial 57 d then switched to the diet providing .45 mg B-6 for the remainder of the experiment (Trt 4). On d 0, 57 and 121 animals from each Trt were killed and samples of the semitendinosus (ST) and semimembranosus (SM) were collected. Following a 24-h chill, the entire SM and ST were dissected from the carcass and weighed Blood was sampled on d 0 and monthly thereafter. The EGOTAc was determined by measuring the glutamate-oxaloacetate transaminase (GOT) activity in isolated, hemolized erythrocytes with and without pyridoxal phosphate added to the reaction mixture.