The use of illicit and misuse of licit drugs is a global public health problem, with illicit drug use being responsible for 1.8% of the total disease burden in Australia in 2011. Oral adverse effects associated with illicit drug use are well-established, with aggressive caries, periodontitis, bruxism, poor oral hygiene and general neglect documented. Other factors such as a high cariogenic diet and lifestyle, social and psychological factors compound the poorer oral health in illicit drug users. Literature has shown that the oral health-related quality of life among injecting drug users is poorer compared with the Australian general population and the overall quality of life of addicted people correlates with caries experience. Thus, the role of the dentist is imperative in managing the oral health of these individuals. Given their widespread recreational use, it is likely that dental practitioners will encounter patients who are regular or past users of illicit drugs. The aim of this article is to describe the prevalence and mechanism of action of commonly used illicit drugs in Australia, including cannabis, methamphetamine, cocaine and heroin and to inform dentists about the common orofacial presentations of their side effects to help with patient management.Abbreviations and acronyms: CBD = cannabidiol; CNS = central nervous system; MA = methamphetamine; ONJ = osteonecrosis of the jaw; THC = delta-9 tetrahydrocannabinol.