This paper reviews the literature on the variation in prescribing patterns and attempts which have been made to relate such variation to characteristics of doctors. Subsequent efforts to identify the correlates of good prescribing are described and the flaws in this approach are highlighted. It is argued that further understanding of prescribing behaviour requires a study of the underlying decision making processes. The literature on three key decisions relating to prescribing is reviewed. Studies of drug adoption and relinquishment from 1966 to 1991 are described. The drug selection process in individual consultations is also discussed and, in particular, the evidence for the ‘drug choice model’ is assessed. Finally, the decision to treat is considered and the lack of empirical evidence in this area is highlighted.