The RETRAN-01 code developed by the Electric Power Research Institute is currently in wide use by the electric utility industry for light water reactor (LWR) system transient thermal-hydraulic analysis. The most attractive qualification method for LWR plant models utilizes direct comparisons with plant transient data. A RETRAN model of the Oconee Nuclear Station [B&W 2568 MW(thermal)] was used to simulate four plant transients. The code demonstrated excellent capability for modeling boundary conditions and control system responses. The close coupling between the primary and secondary systems via the once-through steam generator was successfully simulated.