Introduction: Objectively measuring the effect of primary care process interventions is very challenging. Real time location systems (RTLS) hold the potential to solve this problem. Methods: An outpatient clinic was outfitted with a RTLS based on active-RFID (radiofrequency identification). Staff and patients volunteered to wear RFID transponders which unobtrusively recorded time and location. Wearers were identified only by their role: Patient, MA, RN, MD. The clinical process intervention consisted of reorganizing how medical assistants were utilized from a ad hoc common pool of medical assistants to dedicated assignment of medical assistants. Process measures were recorded before, during and after the intervention. Results: 230 unique patient encounters were recorded from October 2009-January 2010. Eight MDs, 7 MA and 6 RNs participated. Total flow time was significantly decreased while waiting room time was increased. Variance was significantly reduced for both total flow time and face time. In-room wait time and patient face time were decreased, though this did not reach statistical significance. Conclusion: Objectively measuring process change in primary care is feasible using RTLS. In this case the intervention resulted in the waiting room being used more effectively as a process buffer smoothing flow and potentially increasing clinic capacity.