Human hair contains methamphetamine, amitriptyline, imipramine, nicotine, and their metabolites in some amount, which can be detected by routine toxicological methods. Sometimes, the level of drugs reaches over 100 micrograms/g. Animal experiments indicate that these drugs are found solely in sections of hair grown after administration of the drugs. The negative stage after the administration of drugs means that the hair section containing drugs has not come out of the hair follicle. Toxicological examination of the hairs may give some clue helping to identify the chronology of the intoxication.