The main purpose of this study was to detect and quantify modafinil in human urine by gas chromatography-mass spectrometry (GC-MS). Urinary samples were collected from three healthy male volunteers following oral administration of a clinical dose (100 mg) of modafinil (Provigil). Urine specimens were extracted with t-butylmethyl ether (TBME) prior to GC-MS analysis. The results demonstrate that the chromatographic characteristics and the mass spectrum of the unchanged parent drug extracted from urine samples were identical to that obtained from the authentic standard. The times for the unchanged modafinil to reach peak concentration in the urine of the three volunteers were at 2 h (6.14 microg/mL), 4 h (9.93 microg/mL) and 8 h (3.58 microg/mL), respectively. Total clearance occurred in approximately 48-72 h with 2-5% eliminated through urine as unchanged modafinil. The present study demonstrates that modafinil is detectable in the absence of hydrolysis and derivatization steps.