Preliminary data show that hydroxyaniline derivatives have strong inhibitory activities against mushroom tyrosinase. Twelve out of thirty-four synthesized hydroxyaniline derivatives demonstrated inhibitory activities, among which ethyl-(4-hydroxyphenyl)oxamate sodium salt (EHPONa) was found to be the most effective inhibitor. Inhibitory activities of hydroxyaniline derivatives were much higher than that of commercially available whitening agent arbutin, and comparable to that of kojic acid. Data showed that EHPONa x had a higher inhibitory activity of melanin biosynthesis than those of both kojic acid and arbutin. Based on the study of inhibition kinetics and cupric chloride effects on enzyme activity, we propose that 4-hydroxyl oxygen and oxamate oxygen moiety of EHPONa chelate the two cupric ions at the active site, and that phenol moiety interacts with the hydrophobic enzyme pocket. Accordingly, EHPONa may be a good candidate as a skin-whitening agent.