A multitude of diseases will produce areas of increased pigmentation in the skin. These are often a cosmetic liability. These lesions have kept physicians constantly interested in bleaching preparations. As yet no compound has been found which will adequately lighten hyperpigmented skin. The original reports of Oliver and associates that monobenzone caused complete depigmentation naturally aroused interest in this compound. After a number of years of investigation the mode of action of this material is still not clear. Long-term clinical studies have demonstrated that it will not produce uniform, controllable depigmentation. Depigmented areas persist for years and may be permanent.