In understanding and modeling the toxicological and pharmacokinetic properties of organic chemicals, physical-chemical properties such as aqueous solubilities, vapor pressures, and n-octanol/water partition coefficients are required. Currently, the octanol/water partition coefficients (K sub ow's) are limited for chlorinated planar molecules, e.g., dibenzo-p-dioxins, dibenzofurans, biphenylenes, and carbazoles. In the paper, log K sub ow's determined using a reverse phase liquid chromatography/mass spectrometry technique are reported for eight tetrachlorinated planar molecules. In addition, the authors report a reevaluation of log K sub ow's for fifteen polychlorinated dibenzofurans and dibenzo-p-dioxins previously reported by Sarna et al. The reevaluation was performed by using experimental rather than estimated log K sub ow's in the correlative relationship.