The objective of the study is to facilitate the work of West German crime laboratories in analyzing heroin samples quantitatively and qualitatively for the courts. Gas chromatography is used for quantitative and qualitative analysis of the samples. Samples of various types and grades of heroin are examined with and without added calcium carbonate. Results indicate that storage of all the samples at 70 degrees centigrade tends to reduce the diacetylmorphine content of the samples to monacetylmorphine and eventually to morphine. The decomposition rates vary; the diacetylmorphine content of samples with a high concentration of heroin drops about 5 percent a year at a storage temperature of 20 degrees centigrade. Calcium carbonate added in some purification processes appears to contribute to the stability of the heroin quality. High temperatures, humidity, and impurities (e.g., ascorbic acid) from inadequate manufacturing processes speed the decomposition rate of the diacetylmorphine. It is concluded that samples of heroin and other narcotics should be stored in airtight containers at low temperatures to guarantee that analyses can be reproduced and samples compared in crime laboratories over long periods of time. Notes, illustrations, and tables are supplied.