The amounts of penetration of 5 chlorinated solvents through excised rat skin were quantitatively determined by using a multiple phase equilibration method without using chlorinated solvents labelled with radioisotope. The results were compared with those obtained from an in vivo method as previously reported. The penetration rates obtained from the present in vitro method correlated well with those obtained from the in vivo method. Namely, the log-log plot of the in vitro data versus the in vivo data showed a linear relationship, although quantitative agreement between the two sets of data was less than perfect. This systematic comparison of in vitro with in vivo data has shown that the in vitro method for measuring the penetration rate of the chlorinated solvents can reflect the living state.