Human factors methods are rapidly being adopted by the medical informatics community to explore the safety, efficiency, and effectiveness of health information technology (HIT). Although our understanding of how these technologies affect large healthcare organizations is improving, less is known about the context and real-world work practices found in independent primary care practices. This manuscript contains a comprehensive literature review and the results of original research conducted in four primary care practices in Oregon. The goal was to learn: What socio-technical factors shape the way small primary care practices handle external clinical information, and what are the implications for the design of supportive systems?