Abstract: Four metabolites are identified by GC/MS(FI/PCI)in the urine of MDMA addictsand volunteer treated with MDMA. A GC/MS/SIM procedure for determination ofMDMA and its main metabolites MDA, HMMA in urine are also developed, the urinesamples were hydrolyzed with acid or enzyme, and then extracted and derivatized. Themethod is shown to be applicale to determine urine of MDMA addicts.