The Ecstasy and related Drugs Reporting System (EDRS; formerly the ‘Party Drugs Initiative’) 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 supplemented by other data, such as key expert (KE) reports and indicator data, providing a multifaceted approach to monitoring the Australian ecstasy and related drug (ERD) markets. RPU have been identified as a sentinel group of ERD users and provide information on patterns of use, market characteristics, related harms and other issues associated with ERD use. KE are professionals that have regular contact with RPU through their work and 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.