Objective: Recent reports in Europe suggest a decline in 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) use, but quantifiable and objective measurement is unavailable. The global extent of changes in MDMA and related stimulant use is also unclear. This study aims to quantify changes in MDMA use in Australia and determine whether these changes have been accompanied by differing amounts of other stimulant use. Method: We acquired information on recent use of MDMA and related illicit stimulants in Australia using the method of wastewater analysis. Untreated wastewater samples collected from three metropolitan treatment plants in Adelaide from May to July 2009 and the same months in 2010 were analyzed. Concentrations of MDMA, methamphetamine, and benzoylecgonine (a metabolite of cocaine) were determined using solid phase extraction-liquid chromatography- tandem mass spectrometry. Weekly consumed doses of MDMA, methamphetamine, and cocaine per 1,000 people were estimated. Results: From 2009 to 2010, weekly consumption of MDMA decreased from mean of 4.52 (SEM = 0.74) doses/week per 1,000 people to 0.08 (0.01) doses/week per 1,000 people (p <.001); weekly consumption of methamphetamine increased from a mean of 48.35 (6.13) doses/week per 1,000 people to 68.13 (5.33) doses/week per 1,000 people (p <.05); and weekly consumed doses of cocaine did not significantly change. Local roadside saliva testing data also showed that the MDMA-positive test rate decreased from 0.30% to 0.05% and the methamphetaminepositive test rate increased from 1.43% to 1.52% during the past 2 years. Conclusions: This study shows a 50-fold decrease in consumed doses of MDMA with a rise in methamphetamine use in Australia over a 1-year period.