A new and sensitive method to determine ticlopidine in whole human blood using proadifen as the internal standard (IS) is described. The analyte and IS were extracted by solid-phase extraction using Oasis HLB cartridges, and the extracts were analyzed by gas chromatography-electron impact ionisation-mass spectrometry (GC/EI-MS). Calibration curves were established daily in spiked blood samples using a non-linear calibration model, between 0.01 and 4.5 microg/mL. The correlation coefficients were higher than 0.995. Precision and accuracy fulfilled the internationally accepted criteria (coefficients of variation were less than 9%, and the measured concentrations were within +/-7% of the true value). Limits of detection and quantitation were respectively, 3 and 10 ng/mL. No interfering substances were detected by analysis of 10 blank blood samples of different origin. Mean recovery, calculated at three concentration levels, was 71%. Because of its simplicity and speed, the proposed method can be applied in the determination of this inhibitor of platelet aggregation in whole blood samples, and is suitable for application in toxicology routine analysis.