The vapor pressure and solubility (as subcooled liquids) and Henry's Law constants (HLCs) for the individual chlorobiphenyl compounds (CBC) in Aroclor 1242, 1254, and 1260, as well as the HLCs for toxaphene, have been determined with an equilibrium technique. The results were obtained from one set of measurements, for all of the CBC present in the materials of interest, the subcooled organic mixtures that are partitioning in the environment. The HLCs are such that the transport rate of these compounds through the air/water interface should be dependent on both the gas- and liquid-phase mass-transfer coefficients. The solubility of the polychlorinated biphenyls (PCBs) in water is shown to be significantly lower when a solution is prepared by adding an organic solution (acetone, methanol, etc.) of the PCBs to water. These results affect the design and the interpretation of the results from toxicity experiments. (Copyright (c) 1987 American Chemical Society.)