Every institution that participates in NIDA Clinical Trials Network (CTN) research studies must identify an IRB to review and approve those studies. The IRB must follow the requirements of 45 CFR 46 (described in this module) and of the Office for Human Research Protections. Some research sites are under the jurisdiction of two or more IRBs. In these cases, the IRBs may perform joint review, separate review or agree to abide by the review of one of the involved IRBs.