A validation study of RELAP5-3D is performed using data from the Model Boiler Number 2 (MB-2) Prototypical Steam Generator Testing Program. The MB-2 is a 6.67-MW(thermal) power-scaled representation of the Westinghouse Model F steam generator. Comparisons with previous simulations using RELAP5/MOD3.2 are also offered. Limit cycles predicted by the RELAP5/MOD3.2 simulation are reduced in the RELAP5-3D simulation using identical nodalization. Steady-state data from the MB-2 tests used in the validation do not exhibit a limit cycle. The sources of the predicted limit cycles are investigated and feedback mechanisms contributing to the limit cycles are explained.