A method was developed for the screening and quantification of seven amphetamine-type stimulants (ATS) and 22 cathinones, including three metabolites, in urine with Gas Chromatography-Mass Spectrometry. This method allowed the detection and quantification of ATS and cathinones group molecules using one procedure. A study of the stability of the drug mixtures for a period of 201 days in human urine samples under three different conditions has been carried. The ATS and cathinones include amphetamine, methamphetamine, MDA, MDEA, MDMA, PMA, PMMA, cathinone, methcathinone, 3'-position-substituted, ring-substituted, methylenedioxy-substituted, N-alkyl-substituted and pyrrolidinyl-substituted. Twenty drugs out of twenty-nine were validated with a quantitative method. This method can be applied to the nine remaining drugs as a screening method. The linearity of the assay was from 50 to 2000 ng/ml, with limits of detection of 0.5 to 10 ng/ml. In terms of accuracy, between-run and within-run precision were ≤20% for 20 compounds with good selectivity. No carryover was seen, and the recovery was between 80 and 120% for most drugs tested. ATS and pyrrolidinyl-substituted groups were conducted to be stable compounds under all conditions. All compounds tested were stable at -20 °C. Some cathinones were primarily degraded after 21 days at 4 °C. They were detectable but unstable after 201 days at 4 °C. Most cathinones were unstable after a day and completely lost after 28 days at RT.