Given the number of individuals who are dependent on alcohol and/or drugs, it is inevitable that they will present for dental treatment. They are at an increased risk of dental disease for multiple reasons. This paper aims to provide an overview for general dental practitioners (GDPs) of the challenges that can arise in treating such patients, alongside some suggestions for meeting these challenges. General issues are taken into consideration first, then a focus is made on each of the most common substances, together with their implications in dentistry.