As a guide to the rational choice and prescribing of drugs a normative (ideal) problem-solving model has been developed. This model combines medical problem solving and decision analysis, practical medical aspects, and pharmacological facts and basic principles. It consists of a set of actions or steps: determine the goal for treatment, choose a (drug) treatment, start drug treatment, monitor the results, draw conclusions, determine further action, and stop, alter or continue treatment. All steps require several kinds of skills. The cognitive skills needed include the correct use of pharmacological facts and basic principles in the framework of the whole problem-solving process.