Chromatographic analysis by the HPLC technique with Diode Array Detector was employed for MDMA determination. A mobile phase of methanol/water (90:10v/v) allowed a peak signal for MDMA in 16 minutes. Optimized spectrophotometric signal was obtained at a wavelength of 240 nm. The analytical curve from 5.0 to 100.0ppm of MDMA was obtained, showing a linear correlation coefficient of 0.9997 and a detection limit of 2.94ppm. This methodology was employed at the dosage of confiscated samples of ecstasy in the Scientific Police Laboratory of Ribeirão Preto-SP city.