ABSTRACT
It is surprising that so little attention has been paid to what has long been known: most drug misusers take a range of different substances. This simple fact is known to all who work with drug misusers. Yet, perhaps due to the large number of potential combinations of substances and routes of administration, multiple substance use has seldom been the specific topic of research investigations, and its implications have only occasionally been explicitly discussed in the addictions literature. The issue of multiple substance use is more problematic, more complex, and more interesting than is usually assumed.
