Inappropriate prescribing reduces the quality of medical care and leads to a waste of resources. To address these problems, a variety of educational and administrative approaches to improve prescribing have been tried. This article reviews the experiences of the last decade in order to identify which interventions have proven effective in developing countries, and suggests a range of policy options for health planners and managers. Considering the magnitude of resources that are wasted on inappropriately used drugs, many promising interventions are relatively inexpensive. Simple methods are available to monitor drug use in a standardized way and to identify inefficiencies. Intervention approaches that have proved effective in some settings are: standard treatment guidelines; essential drugs lists; pharmacy and therapeutics committees; problem-based basic professional training; and targeted in-service training of health workers. Some other interventions, such as training of drug sellers, education based on group processes and public education, need further testing, but should be supported. Several simplistic approaches have proven ineffective, such as disseminating prescribing information or clinical guidelines in written form only. Two issues that will require a long-term strategic approach are improving prescribing in the private sector and monitoring the impacts of health sector reform. Sufficient evidence is now available to persuade policy-makers that it is possible to promote rational drug use. If such effective strategies are followed, the quality of health care can be improved and drug expenditures reduced.