Toxicokinetic study on organic solvents was carried out using the data obtained by controlled exposure experiments. Organic solvents used in the present study were chlorobenzene, toluene, m-xylene and trichloroethylene. Molar ratio urinary metabolites to organic solvents inhaled was different among solvents and was between 7.7% and 70.8%. The relationship between the amount of exposed toluene and the amount of hippuric acid was linear. However, for m-xylene, the amount of its urinary metabolites was not so much in comparison with the amount of exposed solvent at higher level exposure of 1400ppm × hour. Simulation of the excretion curves of urinary metabolites after cessation of exposure to organic solvents was fit for the two-compartment exponential model. Using the parameters of one compartment model of the single exposure to these organic solvents, the estimated metabolite level curve obtained by repeated exposures could be drawn, and relationship between biological half lives and critical sampling time was discussed. In respect to the urinary metabolites, the excretion rate of metabolites in the urine collected at the end of exposure depended on the period of time from the last urination to the end of exposure.