Although it is known that benzene may be absorbed from inhaled air, the amount that may enter the system by percutaneous absorption is less well established. We have measured the penetration of benzene through human abdominal skin in vitro from solutions in water, gasoline, hexadecane, and isooctane and found permeability constants which averaged 111.0, 1.4, 0.9, and 3.7 X 10(-3) cm X h-1, respectively. The stratum corneum/water partition coefficient for benzene has been measured and averages 30.0. The partition coefficients for the other vehicles are very low and cannot be measured by the method used for water. A new method is presented for calculating these coefficients, however, and they are 0.11, 0.14, 0.17, and 0.19 for gasoline, hexane, isooctane, and hexadecane. The flux of benzene through epidermis in vitro from air saturated with benzene at 31 degrees C averages 1.0 microliter cm-2 X h-1. Solvents may alter the barrier characteristics of the stratum corneum. Polar and nonpolar molecules probably traverse the stratum corneum via different pathways. By measuring the change in the permeability constants for tritiated water (a polar molecule) and for benzene (a relatively nonpolar molecule) before and after exposure to different solvents, alterations of the polar and nonpolar pathways have been shown to differ. Since benzene penetrates normal intact human skin more rapidly than many small organic molecules, and is potentially toxic, the skin should be considered a portal of entry for benzene. Good hygiene should be maintained and care taken to avoid lengthy exposure to solvents containing benzene.