Patient flow in an appointment-based, outpatient internal medicine clinic involving multiple, sequential providers-registrar, triage nurse, physician, and discharger-was studied using computer simulation. Provider task time distributions were obtained through a time-motion study and then input into the computer program, which simulated the clinic situation well. Time interval and sensitivity analyses yielded insights into staffing levels, appointment times, and clinic dynamics. A bottleneck provider was shown, and patient time in the clinic was related to the time of appointment and was slowed by having too many doctors in the clinic. Subsequent operational changes significantly decreased the average observed patient total time in clinic from 75.4 (SD 34.2) minutes to 57.1 (SD 30.2) minutes (p < .001, t test).