The response to a marine oil spill incident in the United States involves mobilization of Federal, State, Local, and Responsible Party (RP)-contracted resources, using the National Incident Management System, Incident Command System (NIMS-ICS). The NIMS-ICS utilizing a Unified Command structure provides a mechanism for responding agencies to establish response priorities and implement cleanup strategies. A recent marine oil spill response in Massachusetts demonstrated that the incorporation of specific state environmental regulatory programs within the NIMS Unified Command system could be a challenging, but advantageous element in the successful cleanup of a marine oil spill. On April 27, 2003, a tank barge grounded in Buzzards Bay, spilling approximately 98,000 gallons of #6 fuel oil. Early in the response, the Massachusetts Department of Environmental Protection (MassDEP), also the State On-Scene Coordinator (SOSC), recognized the importance of utilizing the State'S Licensed Site Professional (LSP) program to assess cleanup effectiveness, characterize residual impacts, and identify clean up endpoints. Massachusetts established the LSP program in 1993 to place greater responsibility for cleaning up sites on the private sector, reduce the burden of approvals on the MassDEP, and to accelerate the cleanup of hazardous wastes sites. The 2003 Buzzards Bay spill was the first time that MassDEP integrated the LSP program into the early stages of a marine oil spill response and the NIMS Unified Command Structure. Including the LSP early in the process also facilitated the transition for conducting LSP-directed clean up after the NIMS Unified Command structure was deactivated. This paper describes the challenges and advantages associated with incorporating a privatized regulatory entity into this well-established and complex organizational matrix. The Massachusetts regulatory structure behind the LSP program is discussed, and recommendations are made for future application of the LSP program in marine oil spill response.