To analyze the root components of compounds causing drug addiction, we have developed our own GC/MS libraries(PESTICID.LIB consisting of 20 pesticides and Herbicides, and DRUG.LIB with 57 drugs). We have usually utilized standardized agents, but gastric contents, gastric specimens, serum and urine samples from patients were also used for the analyses. We were able to add libraries of various difficult to purchase psychotropic drugs and legally restricted agents by extracting them from the patient samples. Comments about the retention time, the base peak of the mass spectrum and 5 typical ion chromatograms in the libraries have been useful for laboratory analysis, and consequently have improved the accuracy of detection and identification. They were also found to be a useful guideline for discrimination of the unchanged materials and the metabolites. We are attempting to improve the accuracy of the library to avoid the effects of GC column conditions such as the column size, column temperature and different inserts by using a retention time index.