|In clinical trials, one differentiates between certain kinds of monitoring: On-site monitoring, remote monitoring, and risk-based monitoring. The most frequently conducted kind is on-site monitoring. For that, the Clinical Research Associate (CRA) needs to be present at the study site. By means of source data verification (SDV) and revision of the investigator site file (ISF), the CRA verifies whether the study site protects the rights and safety of the enrolled patients, laws and regulations are being adhered to, and if the study is being conducted pursuant to GCP and the protocol. In addition, the CRA checks whether the data in the CRF corresponds to the entries in the patient files and whether all adverse events (AEs and SAEs) were completely documented and reported to the sponsor within the appropriate time period. After each monitoring visit, the monitor sends a written report to the sponsor, which contains all essential details. The study site receives a follow-up letter with all pending tasks.