The blood-gas partition coefficients of xenon, reported more than 25 yr ago in the literature, vary considerably from 0.13 to 0.20. Consequently, we have determined this variable by directly injecting xenon-saturated blood into a gas chromatograph-mass spectrometer. This technique yielded a blood-gas partition coefficient for xenon of 0.115 (95% confidence interval 0.107-0.123). The solubility in water measured identically was 0.096, consistent with the reported value of 0.085. These data and a detailed review of the literature strongly suggest that the blood-gas partition coefficient of xenon may be lower than the generally accepted value of 0.14.