Hair samples of psychiatric patients were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS-MS) for the neuroleptics clozapine, flupentixol, haloperidol, penfluridol, thioridazine, and zuclopenthixol. In the study, these neuroleptics were administered to the patients regularly for a minimum of six months. Sample preparation was performed by washing, powdering with a ball mill, extraction of drugs from hair by ultrasonication with methanol, cleanup by solid-phase extraction and subsequent LC-MS-MS analysis using multiple reaction monitoring (MRM). Calibration was performed for all drugs in the range of 0.05 to 10 ng/mg using spiked hair powder and doxepin-d3 as internal standard. Twenty to 50 mg of hair powder was used and the detection limits of LC-MS-MS were below 0.05 ng/mg for all drugs tested. Therapeutic dosage, number of subjects, hair color, and detected amounts of drugs were as follows: clozapine (150400 mg/day; n = 3, light brown, medium brown, black; 0.47-0.92 ng/mg), haloperidol (150 mg/3 weeks; n = 1, black/gray; 12.2 ng/mg), penfluridol (20-30 mg/week; n = 2, medium brown, black; 0.08 ng/mg; not detected in one case), thioridazine (100-400 mg/day; n = 4, light brown, medium brown, black; 0.33-9.91 ng/mg, not detected in one case). Besides the active drugs also the desmethyl-metabolites of clozapine and thioridazine were detected by LC-MS-MS. However, flupentixol (5 mg/day; light brown hair) and zuclopenthixol (350 mg/3 weeks; light brown hair) were not detected by these methods in one case each, although the drugs were administered regularly to these patients. The comparison of dosage and hair color in two cases with thioridazine and penfluridol suggests that other interindividual factors may have an influence on drug concentration in hair.