Abstract: The presence of therapeutic drugs and their metabolites in the hair of psychiatric patients was investigated using GC/EIMS and GC/PCIMS.Nicotine,carbamazepine,amitriptyline,doxepin,trihexyhenidyl,chlorpromazine,chlorprothixene,thifluoperazine,clozapine and haloperidol and their metabolites were found in the hair samples.Chlorpromazine and clozapine concentrations in the hair were found to be dependent on the dosage and their correlation coefficients were 0.8047(P<0.001,n=16) and 0.7097(P<0.001,n=16)respectively.