The stability of opiates in clipped natural human hair was investigated. Hair fibers were incubated with defined solutions of morphine, codeine and dihydrocodeine (pH 7.4) until saturated. Original opiate-positive hair samples collected from drug addicts also were examined. Commercially available bleaching as well as perming formulas (Poly Blonde Ultra, Poly Lock; Henkel, Düsseldorf, Germany) were applied in vitro to the hair strands of both groups under investigation. After these treatments, the drug concentration had decreased for both bleaching and permanent waving. In the spiked hair, only 2-18% of the starting solution could be found after bleaching. About 20-30% of the drug substances could still be detected after perming. In the authentic hair samples, the drug levels of the formerly opiate positive hair fibers had also been reduced but distinct tendencies could not be observed.