Hydroquinone administration in Bufo melanostictus causes an induction of indole amine 2,3-dioxygenase in skin and liver while simultaneously inhibiting tyrosinase in these organs. The result is discussed with the reports of higher urinary excretion of abnormal indole metabolites including derivatives of anthranilic acid in vitiliginous subjects (Roychoudhury and Chakraborty, Clinica. Chim. Acta 22, 298, 1968; Kurbanov and Berezov, Vopr. Med. Khim. 22, 683, 1976).