[EXCERPT] The notion that illicit street drugs, such as heroin, are routinely adulterated or diluted with dangerous substances is a common one. Elsewhere (Coomber, 1997a, 1997b) I have shown that it is in fact a common view of those involved in the treatment of drug users, the policing of drug users, and the research of drug use and related issues, as well as by the users themselves. More importantly, perhaps, it is also believed to be true by the vast majority of those who are deemed to carry out this adulteration/dilution, the drug dealers themselves. The adulteration/dilution of street drugs with dangerous substances is thus, arguably, in normative discursive terms relatively uncontested. It is an assumption that attains the status of a "fact." Within an area (discourses around drugs, their effects and dangers) that is littered with contested meanings and stereotypes, it is one that elicits little discussion or opposition. Recent research, however, suggests that dangerous adulteration/dilution with substances such as brick dust, talcum powder, rat poison, ground lightbulb glass, Vim and Ajax, and numerous other such substances is in fact not a common occurrence, if indeed it happens at all-as opposed to the relatively common practice of adulteration/ dilution of drugs with relatively innocuous substances such as glucose, caffeine and paracetamol. Even the widespread belief that drugs such as Ecstasy are adulterated with "harder" drugs such as heroin is not supported by the forensic evidence or other evidence (Coomber, 1997 a, 1997b). Moreover, the actual practice of adulteration/dilution itself (with any substance) appears not to occur as often as is commonly thought. This paper is concerned with examining how the belief in dangerous adulterants/diluents came into being, why it continues to be assumed at just about all levels of involvement and reporting on drug issues, and how this relative "truth" helps to reinforce other already existing but contested myths upon which it itself is reliant and through which it partially emerged.