This document provides an overview of the key responsibilities of sponsors and contract research organizations (CROs) in clinical trials. It discusses CRO responsibilities in areas such as regulatory affairs, project management, clinical operations, biometrics, medical writing, pharmacovigilance, and quality assurance. For each area, it briefly outlines some of the main tasks involved, such as regulatory submission and approval, clinical monitoring, statistical analysis, safety reporting, and ensuring compliance with Good Clinical Practice standards. The overall purpose is to define the roles that CROs take on to assist sponsors in managing various aspects of clinical research.