This is the second of three papers that review international policies to control spending on drugs and to improve the efficiency of drug use. This paper reviews policies influencing doctors' prescribing of drugs--particularly the use of budgetary restrictions, information and feedback, and guidelines--and evaluates the impact of these policies. Studies evaluating incentive systems are limited, but evidence suggests that providing information on its own will not lead to substantial changes in practice and that more active strategies should be evaluated.