Henry's law constants for 11 polychlorinated biphenyls (PCBs) were measured using a gas purge system at 20 degrees C. The studied PCB congeners ranged from 2,4,4'-trichlorobiphenyl to 2,2',3,4,4',5,5'-heptachlorobiphenyl, spanning a range of hydrophobicities and solubilities, and including four mono-, and seven di-ortho-chlorinated compounds. For four PCBs, Henry's law constants have not been published before. These are 2,3,5,6-tetrachlorobiphenyl, 2,3,4,5,6-pentachlorobiphenyl, 2,2',3,4,4',5-hexachlorobiphenyl, and 2,3,3',4,4', 5 -hexachlorobiphenyl. For the lower chlorinated PCBs, the values are in agreement with available literature data. The values for the higher chlorinated PCBs agreed well with other partitioning data for PCBs and are lower than most available literature data. The measured Henry's law constants decreased with increasing hydrophobicity and showed a high correlation with the number and position of the chlorine atoms. The methods used are suitable for measuring reliable Henry's law constants and also for the higher chlorinated PCB congeners.