The Ecstasy and related Drugs Reporting System (EDRS, formerly the Party Drugs Initiative) arose out of the Illicit Drug Reporting System (IDRS). The EDRS is a study that monitors trends and issues emerging from illicit drug markets in Australia. The data collected examines the price, purity and availability of four primary illicit drug classes – ecstasy, methamphetamine, cocaine and cannabis as well as niche market drugs such as GHB and LSD. Interviews with regular psychostimulant users (RPU) are used to supplement other data, such as key expert (KE) reports and indicator data, thus providing a multifaceted approach to the task of monitoring the Australian ecstasy and related drug (ERD) market. RPU have been identified as a sentinel group of ERD users and are able to provide the required information on patterns of use, market characteristics, related harms and other issues associated with ERD use. KE include nightclub owners, treatment providers and law enforcement personnel. Indicator data include routinely collected health and law enforcement data such as drug related arrests and hospital admissions.