This deposit contains data associated with a study that explores cross-registrations in an existing dataset of clinical trials conducted at German University Medical Centers (UMCs). It primarily includes data files and other files compiled by, or used in the project code repositories: https://github.com/quest-bih/intovalue-crossreg and https://github.com/maia-sh/intovalue-data. This project builds on an existing dataset of clinical trials that involved a UMC in Germany and completed between 2009 - 2017 (for more details, see https://zenodo.org/records/7633995). The deposit contains: Intermediate datasets: This includes data files that were generated in the process of identifying potential EUCTR cross-registrations in the IntoValue dataset. Several approaches were used to identify cross-registered trials: searching for trial registration numbers listed in registrations (`trn-registry-data.rds`), matching on titles from registrations with the amatch function distance 10 (`title-matched-10.rds`), and searching for trial registration numbers listed in related results publications (`trn-publications.rds`). These three datasets were then combined into the intermediate dataset `trn_trn.rds`. Final dataset of potential EUCTR cross-registrations in IntoValue: This includes a final table (`crossreg_pipeline_output.rds`) where each row is a unique registration pair with information on how this registration pair was connected (e.g., title matching). This dataset was used as basis for most analyses in this project. Note: (1) this dataset also includes cross-registrations beyond IntoValue, therefore an initial filtering step is required to obtain the final dataset of EUCTR cross-registrations in IntoValue (see the associated manuscript and code for more details); (2) this datasset is identical to the dataset named `trn_manual_checks.rds` in the code. Manual validation of potential EUCTR cross-registrations: This includes the outcome of the manual screening in a sample of potential EUCTR cross-registrations in IntoValue, specifically: `manual_validation_raw.xlsx`: Raw data of the manual screening. Includes information on whether screened EUCTR cross-registrations could be confirmed, and key characteristics across registrations of the same trial. `manual_validation_processed.csv`: Processed version of `manual_validation_raw.xlsx`. Includes data corrections, data cleaning, and additional derived variables. `sumres.xlsx`: Manual extraction of summary results across registrations of the same trial. Includes all potential EUCTR cross-registrations that were manually screened. Filtering on `is_true_crossreg` for same overall completion status is required.