Accurate information on drug use in communities is essential if health, social and economic harms associated with illicit drug use are to be addressed efficiently. In most countries population drug use is estimated indirectly via surveys, medical presentations and police and custom seizures. All of these methods have at least some problems due to bias, small samples and/or long time delays between collecting the information and analysing the results. Recently the direct quantification of drug residues in wastewater has shown promise as a means of monitoring drug use in defined geographical areas. In this study we measured 3,4-methylenedioxymethamphetamine (MDMA), methamphetamine and benzoylecgonine in sewage inflows in metropolitan and regional areas of Australia and compared these data with published European data. Cocaine use was small compared to European cities (p<0.001) but was compensated for by much greater consumption of methamphetamine (p<0.001) and MDMA (p<0.05). MDMA was more popular in regional areas (p<0.05) whereas methamphetamine and cocaine were mainly consumed in the city (p<0.05). Greater than 5-fold increases in MDMA use were detected on weekends (p<0.001). This approach has the potential to improve our understanding of drug use in populations and should be further developed to improve prevention and treatment programs.