OBJECTIVE: To document the Institutional Review Board (IRB) review process and to explore the impact of different patient notification procedures. DATA SOURCES/STUDY SETTING: Review of IRB application and correspondence records prospectively collected during a multisite study of health care quality involving telephone interviews of 3,000 participants across 15 primary care sites. STUDY DESIGN: Records were reviewed to ascertain: (1) the type of IRB review conducted, (2) the number of days from submission to approval of the IRB application, (3) whether the IRB required patient notification and/or consent prior to the release of names, and (4) patient participation rates. DATA COLLECTION/EXTRACTION METHODS: The study coordinating center prepared a common study protocol for IRB submission and assisted sites with submission. The application, correspondence with the IRB, consent script, and patient letters were collected, reviewed, coded, and analyzed. PRINCIPAL FINDINGS: IRBs at the 15 sites and survey center varied in the type of IRB required and the number of days from submission to approval (range of 5-172 days). Four sites required patient notification in advance of the study; 2-11 percent of patients refused in opt-out sites and 37 percent in the single opt-in site. Participation among contacted patients did not appear to be related to patient notification procedures. CONCLUSIONS: Variations in IRB requirements can affect response rates and sample generalizability.