Despite acceptance of the essential drug concept by over 100 countries, current drug use patterns frequently result in unsafe use, waste of scarce resources, non-compliance, excess adverse drug reactions and disease resistance. Even in countries where resources for research are available, most efforts to improve drug prescribing have never been properly evaluated. Proposed interventions should reflect the behavioral basis for current drug use, target priority public health areas, and be feasible in developing country contexts. Most importantly, they must be critically assessed for cost and effectiveness in well-controlled field trials. The International Network for Rational Use of Drugs (INRUD) is a cooperative organization of health professionals and researchers in developing countries whose aim is to promote improved quality of care through more clinically effective and economically efficient use of pharmaceuticals. To accomplish this, INRUD will strengthen regional and national capacities to develop and scientifically evaluate programs to improve drug use and disseminate information on practical strategies shown to be cost-effective.