The interaction of the dihydroxyanthraquinones, emodin (1), aloe-emodin (2), and rhein (3) with human serum albumin (HSA) has been studied through fluorescence spectroscopy. Quenching studies and the association constant of the anthraquinoid compounds 1, 2, and 3 in the presence of HSA were estimated. The binding and quenching studies suggest that only emodin (1) may serve as a useful fluorescence probe for structure/function studies of different emodin binding proteins. No photoinduced binding was observed after irradiation of compounds 1, 2, and 3 in presence of human serum albumin.