Prior research has demonstrated that clinicians often fail to review and act upon outpatient test results in a timely and appropriate manner. To address this patient safety and quality of care issue, Partners Healthcare has developed a browser-based, provider-centric, comprehensive results management application to help clinic physicians review and act upon test results in a safe, reliable, and efficient manner. The application, called the Results Manager, incorporates extensive decision support features to classify the degree of abnormality for each result, presents guidelines to help clinicians manage abnormal results, allows clinicians to generate result letters to patients with predefined, context-sensitive templates and prompts physicians to set reminders for future testing. In this paper, we outline the design process and functionality of Results Manager. We also discuss its underlying architectural design, which revolves around a clinical event monitor and a rules engine, and the methodological challenges encountered in designing this application.