This manuscript addresses the development and operating procedures of the Cystic Fibrosis Foundation Data Safety Monitoring Board (CFF-DSMB) and its role in the development and approval of new therapies through complex clinical trials with an emphasis on ensuring patient safety and study integrity. The authors describe the processes that have been developed over the last 25 years including the development of educational curricula for DSMB members and patient representation on DSMBs. The experience and success of the CFF-DSMB can serve as a model for providing high quality oversight of clinical trials for other groups who are dedicated to developing treatments for rare and complex diseases.