For many years, it was interested to study the effect of protein or amino acids contents of daily diet on the V. B₆ requirement, since vitamin B₆ has important roles on the metabolism of nutrition components, specially amino acid.<BR>In this study rats fed on the diet that was supplemented 2% excess dl-methionine,1.6% excess l-cystine or 2.2% excess l-tyrosine for four weeks was determined those liver pyridoxal phosphate content and enzyme activities concerned the pyridoxal phosphate formation. After the initial temporary increase, the liver pyridoxal phosphate content decreased since third day, gradually recovered and was equilibrated on a little increased value for normal one at the end of third week. It seemed that this variation of liver pyridoxal phosphate content was given by the change of the pyridoxal kinase activity (the pyridoxal kinase is one enzyme concerned pyridoxal phosphate formation). The activity of pyridoxine phosphate oxidase was simultaneous assayed, but no change was found.<BR>Cerecedo et al. reported that vitamin B₆ deficient rats fed on this amino acids supplemented diet indicated the early appearance of deficient symptom, but not on other amino acids supplemented diet. But in this study, dl-methionine, l-cystine and l-tyrosine gave a similar effect on liver pyridoxal phosphate content.<BR>For the initial temporary increase in the liver pyridoxal phosphate content and pyridoxal kinase activity, it was suggested to adapt the change of diet components. Then the hormonal effect of the initial temporary increase in liver pyridoxal phosphate content and pyridoxal kinase activity was investigated. The cortisone injection independently effected to increase them. Both adrenalectomized and pituitarectomized rats were also determined. Based on those investigations, the initial temporary increases in liver pyridoxal phosphate content and pyridoxal kinase activity were suggested to be effected with adrenals.