Epinochrome (5) has been shown to react with thioglycollic acid to give mainly 5,6-dihydroxy-1-methylindoline and a 4-thiosubstituted 5,6-dihydroxy-1-methylindoline. The acetyl derivatives of these compounds (i.e. 7b and 15), along with that of the corresponding 4-thiosubstituted 5,6-dihydroxyindole (i.e. 11), were isolated after acetylation of the reaction mixture. The latter compound is probably a secondary product of the reaction, having arisen from the 4-thiosubstituted 5,6-dihydroxy-1-methylindoline which is formed initially.