Overview of practice-based research networks (PBRNs) and 16 office practices ceding to a lead institutional review board (IRB). COMIRB, Colorado Multiple Institutional Review Board; IAA, IRB Authorization Agreement; IRENE, Iowa Research Network; ORPRN, Oregon Rural Practice-based Research Network; PI, principal investigator; SNOCAP, State Networks of Colorado Ambulatory Practices and Partners; WREN, Wisconsin Research and Education Network.