Regular and timely review appraisal and communication of safety information are critical to risk management during the clinical development of drugs. Whereas the overall goal of a clinical development program is to characterize the benefit-risk relationship of the product in a particular patient population, the risk to individual trial subjects is a critical consideration during product development at a time when the effectiveness of a product is generally uncertain. By conducting an overall appraisal of safety data at regular intervals, risks can be recognized thoughtfully assessed and appropriately communicated to all interested stakeholders to support the safety of clinical trial subjects. Although regulatory authorities currently require the submission of a periodic safety report during the conduct of clinical trials, there are substantial differences in the format content and timing of the different reports. The CIOMS VII Working group is proposing in this new publication an internationally harmonized document namely the Development Safety Update Report (DSUR) that is modeled after the Periodic Safety Update Report (PSUR) for marketed products. It presents the general principles behind the preparation and use of the DSUR and a model DSUR. The model is illustrated with sample fictitious DSURs for a commercial and non-commercial (trial-specific) sponsor.