In many medical indications clinical research is organized within study groups which provide and maintain the clinical infrastructure for their randomized clinical trials. Each group also manages a data center where high quality databases store the study specific individual patient data. Sharing this data between study groups is not straightforward. Therefore, a concept is needed which allows to represent a detailed overview on the information available across the cooperating groups. We propose a metadata based patient register and describe a first prototype. It provides information about available patient data sets to interested research partners while the typical register approach only collects a predefined limited core data set. This register implementation enables cooperative groups to allocate clinical data for future research projects in distributed data sources beyond the restrictions of core data sets. Additionally, it supports the research network in communication and data standardization and complies with a governance structure which is compatible with ethical aspects, privacy protection, and patient rights.