Melanogenesis is a physiological process resulting in the synthesis of melanin pigments, which play a crucial protective role against skin photocarcinogenesis. The heart wood of Caesalpinia sappan L.(C. sappan) has long been commonly used in Oriental folk medicines to promote blood circulation, and as an emmenagogue, analgesic or anti-inflammatory agent as well as a remedy for thrombosis. From the heartwood, many constituents have been purified and among them, brazilin and hematoxylin are two of the most abundant. This present study was designed to investigate the inhibitory effect of butanol extract from C. sappan on proliferation and melanogenesis in Melan-a cells. After 48 h treatment of these cells with various concentrations of butanol extract, the cells showed a dose-dependent inhibition in their proliferation without apoptotic cell death. Therefore, the growth retardation by the extract may be due to the cell arrest or cell differentiation. We also estimated total melanin content as a final product and activity of tyrosinase, a key enzyme, of melanogenesis in Melan-a cells. The melanin content and tyrosinase activity were deσeased in extract-treated cells in a dose dependent manner compared to control group. The butanol extract also resulted in a decrease of melanin content in ${alpha}-melanocyte-stimulating$ hormone (MSH)-induced melanogenesis, indicating that butanol extract of C. sappan could be developed as skin whitening components of cosmetics.