BACKGROUND: The Northern New England Cardiovascular Disease Study Group, a voluntary regional consortium, includes all cardiothoracic surgeons and interventional cardiologists, as well as nurses, anesthesiologists, perfusionists, administrators, and scientists associated with the six medical centers in Maine, New Hampshire, and Vermont and one Massachusetts-based medical center that support coronary artery bypass graft (CABG) surgery and percutaneous coronary interventions (PCI). Since 1987 the group has met at least three times a year to foster improvements in patient care. PROGRESS IN THE STUDY OF CABG SURGERY: The group's activities have included continued monitoring of outcomes, training in continuous quality improvement, and a benchmarking effort that allowed institutions to learn from one another. In the postintervention period (mid-1991 through early 1992) there were 293 fewer deaths (n = 575) than the 868 expected. In 1995 a new cycle of quality improvement work aimed at identifying the causes and correlates of postoperative mortality began. Study groups for each institution were organized to examine issues related to death from low-output states. PROGRESS IN THE STUDY OF PCIS: Major improvement in hospital outcomes have occurred in relation to the improving technology (primarily coronary stenting). Near-twofold variability in the use of stents has led to vigorous discussions about the role of new devices. LESSONS LEARNED: Randomized clinical trials are very important to assessing the effects of specific treatments, but most of what is known about actual clinical care will come from observational studies. Demonstrating the variability in practice patterns can be a potent stimulus to try to answer the important questions.