As part of a larger project studying the neurobehavioral effects of solvents both in single exposures and in combination, a group of 70 healthy male and female subjects were assigned randomly to four treatment conditions: chemical placebo, 250 parts per million (ppm) acetone (67641), 200ppm methyl-ethyl-ketone (78933) (MEK), or a combination of 125ppm acetone and 100ppm MEK, with exposures lasting 4 hours. Samples of expired air, venous blood, and urine were collected before exposure, 2 hours into the exposure, and at various times after the exposure. The average blood concentrations of acetone or MEK were still rising after the 4 hour exposure. The time course for the solvent concentrations in blood was similar to that of the breath concentrations, and there was a correlation between solvent blood levels and the concentration of the solvent in expired air. MEK was more rapidly cleared from the body following exposure than was acetone. There was a consistent trend toward lower blood concentrations in females for both solvents, but these differences were not statistically significant. The experimental results were discussed in relation to physiological simulation modeling of the exposure. The authors conclude that the data support an additive model for the body burden of acetone combined with MEK.