MELCOR is a fully integrated computer code that models all phases of the progression of severe accidents in light water reactor (LWR) nuclear power plants and is being developed for the U.S. Nuclear Regulatory Commission (NRC) by Sandia National Laboratories. Brookhaven National Laboratory (BNL) has a program with the NRC called “MELCOR Verification, Benchmarking, and Applications,” the aim of which is to provide independent assessment of MELCOR as a severe accident thermal-hydraulic/source term analysis tool. The scope of this program is to perform quality control verification on all released versions of MELCOR, to benchmark MELCOR against more mechanistic codes and experimental data from severe fuel damage tests, and to evaluate the ability of MELCOR to simulate long-term severe accident transients in commercial LWRs, by applying the code to model both boiling water reactors and pressurized water reactors. Under this program, BNL provided input to the NRC-sponsored MELCOR Peer Review and is currently contributing to the MELCOR Cooperative Assessment Program (MCAP). A summary of MELCOR assessment efforts at BNL and their contribution to NRC goals with respect to MELCOR is presented.