Fleischhauer1reported in 1930 that Liantral, an extract of anthracite coal tar, sensitized human skin to both artificial and natural ultraviolet light. Later studies, however, carried out at the University of Oklahoma2using Liquor Carbonis Detergens (hereafter called LCD) and ultraviolet light, indicated that the LCD acted as a screen and failed to sensitize normal human skin to ultraviolet light. It was our desire to examine, first, whether coal tar sensitization was produced by sunlight and not by hot quartz radiation, and, second, to determine whether Liantral and LCD, which are by-products of anthracite coal and bituminous coal respectively, have different effects on human skin. The latter seemed plausible since coal is a highly complex material containing hundreds of discrete compounds or combinations of compounds, many of which have not as yet been isolated.3According to Duke Laboratories,4analysis of raw anthracite coal tar has indicated