A biological monitoring method for urinary dichloromethane (DCM) has been developed by using head-space gas chromatography with FID detection. The calibration curve is linear in a wide range of DCM levels between 0.01 and 2 mg/l. The recovery rate is almost 100% and within-run coefficients of variation are 2.9-3.7%. A highly significant correlation is found between exposure levels and urinary concentrations of DCM. Determination of urine DCM by this method has many advantages such as sample storage, no need for correction of urine concentration, absence of gender difference and also no confounding effect of glutathione S-transferase T1 polymorphism.