A high-performance liquid chromatographic method with ultraviolet radiation absorbance detection has been developed for the determination of the principal opiates (heroin, 6-monoacetylmorphine, morphine, codeine) in human hair. An amount of 100 mg hair was incubated with 2 mL HCl 0.1 M at 56°C overnight and it was then extracted by solid-phase extraction using reversed-phase/ion exchange cartridges. Chromatography has been performed using a C18reversed-phase column with a mobile phase consisting of water-acetonitrile (70:30 v/v) containing 0.01 M NaH2PO4and 0.002 M sodium laurylsulphate at a final pH of 2.1. The linearity of the method was obtained in the concentration range of 0.5-50 ng/mg hair for 6-monoacetylmorphine, morphine and codeine, and of 5–200 ng/mg hair for heroin. The accuracy of the methodology was assessed using reference material from National Institute of Standards and Technology consisting of human hair segments and powdered human hair soaked with opiates.