Patient registries are a useful tool to measure outcomes and compare the effectiveness of therapies in a specific patient population. High data quality and completeness are therefore advantageous for registry analysis. Data integration from multiple sources may increase completeness of the data. The pediatric renal transplantation registry CERTAIN identified Eurotransplant (ET) and the Collaborative Transplant Study (CTS) as possible partners for data exchange. Import and export interfaces with CTS and ET were implemented. All parties reached their projected goals and benefit from the exchange.