In rats showing impaired growth and liver enlargement from riboflavin deficiency there was a decrease in the weights of thymus and spleen and a slight increase in the weight of adrenals, but these were also shown by control rats with the same degree of growth impairment from inanition. There was no effect upon the ascorbic acid content of the adrenals, and a questionable effect upon their cholesterol content. There was some decrease in the number of circulating lymphocytes. There was a decrease in the catalase activity of the liver, but this was complicated by a relationship to the amount of dietary protein. These observations oppose the concept that in riboflavin deficiency adrenal cortical function is impaired, and suggest that it is slightly stimulated.