200P rimary care clinicians face a daunting set of challenges in today's health care environment. Health care reform is creating a constantly evolving context for providing care. Time and productivity pressures contrast with a growing set of clinical expectations and responsibilities in the patient encounter. Chronic and behavioral conditions increasingly dominate the lives of our patients, yet we have a limited set of tools for making consistent and meaningful improvement in the trajectory of these diseases. At the same time, patients can fi nd it diffi cult to adopt truly effective preventive or early intervention tools. Underlying all of these issues is the role of socioeconomic and community factors in the conditions that we see.In response, primary care researchers have sought and tested new ideas by which clinicians can meet these challenges. In so doing, these researchers have established a strong record of innovation-and of respect for persons and communities. Examples include the use of multimethod research to understand processes in primary care, the use of practice-based research networks for testing interventions in real-world settings, and the use of complexity science concepts in understanding care delivery.1-3 Primary care researchers have also been leaders in advocating the importance of respectful partnerships with communities in the search for new solutions to the challenges we face. 4 The article by Shaw et al in this issue of the Annals extends this record of innovation and respectfulness of family medicine researchers. 5 This research team designed a state-of-the-art, cluster randomized trial of a strategy to increase the proportion of patients in practices who had received up-to-date screening for colorectal cancer. Conducted in a practice-based research network, the intervention included multimethod practice assessment, followed by within-practice teams engaged in refl ective adaptive processes strategizing improvements in screening, and by crosspractice learning collaboratives. The analysis showed a nonsignifi cant trend toward greater net increase in screening rates of intervention compared with control practices. Although the overall rate of screening was the primary outcome in this trial in which individual practices were the unit of study (whole practices received either the intervention or control condition), this analysis appeared to obscure important effect modifi cation. That is, some practices in the intervention group got much better while, surprisingly, at least 1 intervention practice's overall screening rate got much worse.There are several possible explanations for this surprising fi nding. It could represent concurrent, unrelated changes in the practice, such as staff turnover. It could represent normal statistical variation-some practices randomly improve while some randomly worsen. It could refl ect a delayed response to changes in screening approaches in the practice. As Shaw et al note, however, the disturbing possibility is that the worsened screening rates could repre...