This document discusses the investigation of medicinal product dossiers (IMPDs) which are required for clinical trial approval in the European Union. There are two main steps for drug approval: clinical trial application and marketing authorization application. IMPDs contain information about the investigational medicinal product including protocols, informed consent forms, and risk management plans. IMPDs can be full or simplified depending on previous submissions. An investigator brochure is also required and provides clinical and non-clinical data on the investigational product to investigators. It differs from an IMPD which focuses more on development and manufacturing details.