A quantitative method to determine the solubility of polychlorinated biphenyls (PCBs) and used capacitor fluid in water was developed employing high-resolution glass capillary–column gas chromatography. The response of the electron capture detector to mono-,di-,tri- and tetra-chlorobiphenyls and an internal standard were use to estimate the solubility of the PCBs. Results of the rate of dissolution of Aroclor 1242 and used capacitor fluid in water indicated that a period of five months was required to reach equilibrium. The water-soluble fractions of Aroclor 1242 and used capacitor fluid (Aroclor 1242-impregnated) were found to be identical. Certain isomers of the mono-, di- and poly-biphenyls in Aroclor 1242 were relatively soluble and were identified as 2-mono-, 2,4′-di-, 2,5,2′-tri, 2,3,2′-tri, 2,5,4′-tri, 2,5,2′,5′-tetra, 2,4,2′,5′-tetra, 2,4,2′,4′-tetra-, 2,3,2′,5′-tetra- and 2,4,3′,4′-tetra-chlorobiphenyl. In general, the water-soluble fractions of the PCB mixtures were richer in the lower chlorinated isomers than the original PCB mixtures. The solubilities of Aroclor 1016, 1221, 1242, and 1254 were 906, 3516, 703, and ~70 ug1-1, respectively, whereas the solubility of the used capacitor fluid was the same as that of Aroclor 1242.