To help clinicians care for patients with HIV infection, we developed an interactive knowledge-based electronic patient record that integrates rule-based decision support and full-text information retrieval with an online patient record. This highly interactive clinical workstation now allows the clinicians at a large primary care practice (30,000 ambulatory visits per year) to use online information resources and fully electronic patient records during all patient encounters. The resulting practice database is continually updated with outcome data on a cohort of 700 patients with HIV infection. As a byproduct of this integrated system, we have developed improved statistical methods to measure the effects of electronic alerts and reminders.