Selecting the right Clinical Research Organization (CRO) is vital to the success of any clinical study. Get it right and the months that follow will be that much more enjoyable because the study is more likely to run smoothly and stay within budget. Those sponsors who have had to transition a clinical study away from a poorly performing CRO to an alternative supplier, mid-study, will be acutely aware of the pain that this can cause and the need for a thorough vendor selection process. The Request For Proposal (RFP) is a vital component of that process. A well-defined and comprehensive RFP creates the best chance of selecting the most appropriate CRO, or combination of CROs, to complete the project.