The melanin content of liver of male toad was altered by testosterone injection. A single injection of testosterone at a dose of 1 microgram/g or 2 microgram/g of body weight caused an increase in melanin content of liver of male toad on the 3rd and 5th day after injection. With lower doses (0.1 microgram/g and 0.5 microgram/g), however, there was no alteration of melanin content of liver. Compared to the results obtained with 1 microgram of testosterone per g of body weight, the degree of response with respect to the melanin content with 2 microgram/g tended to be higher, but the difference was not statistically significant. The female toads remained unaffected with respect to melanin content of liver with these doses of testosterone used.