Discrete-event simulation can be used as an effective tool for healthcare administrators to "test" various operational decisions. The recent growth in hospital outpatient volumes and a constrained financial environment make discrete-event simulation a cost-effective way to diagnose inefficiency and create and test strategies for improvement. This study shows how discrete-event simulation was used in an adult medicine clinic within a large, tertiary care, academic medical center. Simulation creation steps are discussed, including information gathering, process mapping, data collection, model creation, and results. Results of the simulation indicated that system bottle-necks were present in the medication administration and check-out steps of the clinic process. The simulation predicted that matching resources to excessive demand at appropriate times for these bottleneck steps would reduce patients' mean time in the system (i.e., visit time) from 124.3 (s.d. +/- 65.7) minutes to 87.0 (s.d. +/- 36.4) minutes. Although other factors may affect real-world operations of a clinic, discrete-event simulation allows healthcare administrators and clinic operational decision makers to observe the effects of changing staffing and resource allocations on patient wait and throughput time. Discrete-event simulation is not a cure-all for clinic throughput problems, but can be a strong tool to provide evidentiary guidance for clinic operational redesign.