A sensitive and reproducible method for the quantitative determination of cathinone (CTN), norpseudoephedrine (NPE, cathine) and norephedrine (NE) from hair was developed. The compounds were extracted for 4 hours with phosphate buffer pH 2.0, followed by a standard solid phase extraction procedure on a mixed phase column, derivatization with heptafluorobutyric anhydride (HFBA) and GC–MS separation and quantification using D 3-ephedrine (D 3-E) and α-aminoacetophenone (AAP) as the internal standards. The diastereomers NPE and NE were satisfactorily separated. In the validation, the limits of detection and of quantification were determined at 0.03–0.08 ng/mg and 0.10–0.24 ng/mg, respectively and the interday standard deviation was between 10 and 15%. The method was applied to hair samples of 24 Yemenite khat chewers. All three compounds were detected in 23 of these cases. The concentrations ranged from 0.57 to 23.9 ng/mg for NPE, 0.19–25.0 ng/mg for NE and 0.11–22.7 ng/mg for CTN. A highly significant correlation was found between the self-reported data about the khat consumption habits of the volunteers (4–56 h chewing per week) and the concentrations of norephedrine and norpseudoephedrine in hair.