Male rats maintained on a diet in which the vitamin A alcohol had been replaced by vitamin A acid developed lesions in the reproductive tract. The testicular changes were a sloughing of the cells of the germinal epithelium followed by an obliteration of the lumen of the tubule by Sertoli cells. Testicular regeneration was produced by the administration of vitamin A alcohol. The lesions are comparable to those of vitamin A deficiency as described by Mason (1933) but are uncomplicated by the secondary manifestations of vitamin A deficiency. The present paper also describes for the first time lesions in the testes of healthy growing prepubertal rats fed the vitamin A acid diet.