Postmarketing surveillance-one of the key issues in drug development.

The terms "postmarketing surveillance" or "human phase IV studies" are applied to all those examinations which are performed with a drug following its registration. The principles, methods of these examinations are discussed on the basis of international experiences. The authors also give some examples from Hungarian practice referring to this subject. They consider postmarketing examinations to be as important as the clinical pharmacological examinations preceding the introduction of a drug. The usefulness, role of a drug in the therapy may be definitely determined on the basis of the results of these studies.