There are six responsibilities of the NMSS. These responsibilities include: 1) licensing of fuel cycle facilities, 2) licensing of nuclear materials for uses other than in reactors, 3) regulation of the transportation of the nuclear materials, 4) safeguarding of nuclear materials from sabotage and diversion to authorized uses, 5) regulation of radioactive waste disposal facilities, and 6) regulation of the decommissioning of previously licensed nuclear facilities that are no longer in use. This paper reviews each of these functions. The final section includes information on where additional information can be obtained on non-reactor NRC licenses.