In order to prove the intake of a newly encountered designer drug, Methylone, a sensitive and useful method, which allows us to simultaneously detect Methylone and its metabolites in human urine, has been established by means of a combination of gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI MS). GC-MS accompanied with trifluoroacetyl (TFA) derivatization and LC-MS analyses were performed following acid hydrolysis and liquid-liquid extraction with a chloroform-2-propanol mixture (3:1, v/v). Methylone and its metabolites, 3,4-methylenedioxycathinone (MDC), 4-hydroxy-3-methoxymethcathinone (HMMC) and 3-hydroxy-4-methoxymethcathinone (3-OH-4-MeO-MC) could be satisfactorily separated on a semi-micro ODS column using linear gradient elution with a binary mobile phase of methanol and 10 mM ammonium formate buffer (pH 3.5).   The detection limits of the four analytes by GC-MS were over the range of 5-25 ng/ml in a scan mode, and 0.5-2.5 ng/ml in a selected ion monitoring (SIM) mode. Upon applying the LC-ESI MS technique, the linear calibration curves were obtained using the SIM mode in the range of 25-500 ng/ml for Methylone, HMMC and 3-OH-4-MeO-MC, and 50-1000 ng/ml for MDC. The detection limits were over the range of 25-100 ng/ml in the scan mode, and 2.5-25 ng/ml in the SIM mode.   Because of its high sensitivity, this analytical procedure will be applicable for proof of Methylone intake in forensic toxicology and clinical chemistry.