Deficiency symptoms of B vitamins were observed under the Japanese field conditions among the meat-type chicks imported recently for the purpose of broiler production. Accordingly, the requirements of thiamine, riboflavin, pyridoxine, niacin and choline for White Rock chicks, the third generation of chicks imported from Abor Acore Farms, U.S.A., were studied and from the growth rate and deficiency symptoms it was found that the higher dietary levels of riboflavin, niacin and choline than those recommended by National Research Council, U.S.A., were required by the chicks. In the second experiment, niacin-deficient diets with an addition of graded levels of niacin were fed to the same White Rock chicks for 3 weeks. Linear relationship between body weight gain and logarithm of dietary niacin level was observed. The intersection of the regression line and y=200.3g, i. e. the average gain of chicks fed much excess of niacin, gave the estimate of niacin requirement. This was 30 mg/kg diet, or 1.1 times more than the recommended level.