cal practice.9The first US PBRNs were regional primary care networks that emerged in the 1970s.36 Although most AHRQ-registered PBRNs focus on primary care, a wide variety of PBRNs focus on areas including dentistry, pharmacy, and chiropractic.37 In addition to their different foci, PBRNs vary widely in their size, geographic reach (local versus national), and the sophistication of the research in