the literature on drug addiction has grown at a rate that defies anyone to keep abreast of the literature, and apparently in inverse proportion to our understanding of the subject. Addiction, or dependence, as it is more fashionable to call it , excites controversy and speculation yet true understanding of the phenomenon remains elusive. In fact the area is fraught with speculation and acrimonious debate. Definition of terms such as "drug","addiction", and "abuse" is obviously less controversial than attempts to explain the nature of drug dependence, yet ever the terminology is imprecise and overlain with subjective connotation. At its most basic,a drug, as defined by the World Heath Organization, is simply "any substance which when taken into the living organism may modify one or more of its functions". this kind of definition is too wide to be of any use in a discussion of dependence: it covers everything from insulin to aspirin,penicillin to alcohol.