The theoretical ratio of heroin to acetylcodeine doubles at each stage of the chemical conversion in the series opium-morphine-heroin. When opium samples of known origin were examined for ratios of heroin to acetylcodeine, they showed variations that enabled the reseacher to develop distinct composition profiles of the alkaloids for each geographical area studies. The profiles enable comparisons between heroin samples of known origin and illicit heroin samples of unknown origin, thus enabling identification of the geographical origin of the illicit heroin samples. The identification method can also be used to identify the origin of illicit morphine samples. 14 references. (Author abstract modified)