A gas chromatographic method for simultaneously determining methyl- ethyl-ketone (78933) (MEK), toluene (108883), and ethanol (64175) in blood was described. A 0.25 milliliter (ml) sample of heparinized blood was drawn into a 7ml glass screw cap vial to which 0.5ml dextrose solution and 0.25ml isobutanol were added. The isobutanol served as an internal standard. After mixing on a rotator for 15 minutes, the samples were heated at 60 degrees-C for 15 minutes. A 1ml sample of the vapor inside the sealed vial was removed with a gas tight syringe heated to 60 degrees and was injected into the head space of a gas chromatograph with a flame ionization detector. The concentrations of MEK, toluene, and ethanol in the sample were determined from calibration curves. The method could be used for blood samples containing 0.1 to 1.8 micrograms per milliliter (microg/ml) MEK, 1 to 600microg/ml toluene, and 10 to 600microg/ml ethanol. The detection limits for MEK, toluene, and ethanol were deviations for ten replicate determinations of a sample containing 1microg/ml MEK and toluene and 10microg/ml ethanol were 9.5, 9.8, and 5.6 percent, respectively. In recovery experiments using blood samples spiked with 2microg/ml MEK and toluene and 50microg/ml ethanol, recoveries of 90 to 98 percent were obtained. The author notes that the method is useful for monitoring simultaneous exposures to MEK, toluene, and ethanol under controlled, experimental conditions.