Oral administration of metanil yellow (MY) at 3.0% (w/w) dose level to adult male albino rats maintained on low protein (LP) diet for 30 days resulted in a greater decrease in absolute and relative weights of testes than in those rats maintained on a normal protein (NP)diet. A marked decrease in the activities of lactate dehydrogenase and hyaluronidase and content of lactic acid in LP + MY fed animals suggested that low protein diet enhenced the vulnerability of germ cells towards metanil yellow. The lack of significant changes in the cholesterol content of testis, the fructose content of the coagulating glands and the dorsolateral prostate,the activities of aIkaline phosphatase in the seminal vesicle, and acid phosphatase in ventral prostate of the MY treated animals suggested that their androgenic status were not affected. Oral administration of metanil yellow (MY) at 3.0% (w / w) dose level to adult male albino rats maintained on low protein (LP) diet for 30 days resulted in a greater decrease in absolute and relative weights of testes than in rats rats A marked decrease in the activities of lactate dehydrogenase and hyaluronidase and content of lactic acid in LP + MY fed animals suggested that low protein diet enhenced the vulnerability of germ cells to metanil yellow. The lack of significant changes in the cholesterol content of testis, the fructose content of the coagulating glands and the dorsolateral prostate, the activities of a Ikaline phosphatase in the seminal vesicle, and acid phosphatase in ventral prostate of the MY of Animals of suggested that their androgenic status were not affected .