Substance misuse, particularly alcohol and prescription drugs, in elderly people is a common but under-recognised problem with significant negative impacts on the physical and psychological health and quality of life. More older people than ever are reporting that they have had experiences with drugs at some point in their lives, and drug problems have no age limits. In addition, binge drinking is also common in older people. Despite the emergence of a cohort of recreational and dependent addicts in the elderly, there is limited data on the prevalence of illicit substance misuse. Tobacco is the most commonly used psychoactive substance among older people. The over-60s are also more likely than younger people to have smoked at some time in their lives; however, they are more likely than younger people to have given up. Homelessness is an increasing problem on a global scale, especially with those who have a history of problematic substance misuse. Substance misuse is often both a cause and a result of homelessness, often arising after people lose their housing. The majority of homeless alcohol and substance misusers do not use traditional primary health care services.