Good clinical practice (GCP) includes protection of the involved patients/volunteers and quality of the clinical documentation which forms the basis for registration of a preparation. During recent years, guidelines for GCP have been presented from various quarters. These describe the requirements which must be fulfilled to document the effect and safety of a new preparation. The requirements comprise involvement of the investigator and also of the monitor and sponsor and ethical committees. In this article, the contents of the guidelines are reviewed and the significance these obtain of the involved parts in the clinical development of medicinal preparations.