BACKGROUND Illicit drug use is common in Australia, with nearly 40% of Australians having tried an illicit substance in their lifetime. While cannabis is by far the most prevalent substance used, heroin and other opiates contribute to over 90% of deaths associated with illicit drug use. OBJECTIVE This article describes the current epidemiology and harms related to illicit drug use, and outlines the principles in the management of acute overdose. CONCLUSIONS The acute management of a suspected overdose involves the identification of the toxicants by taking a careful history accompanied by a focused physical examination. An understanding of the pharmacological profile of the illicit drug and its corresponding toxidrome is essential in providing acute care before referral to emergency medical services.