Abstract: Role-based access control (RBAC) is implemented on an multi-level secure (MLS) system by establishing a relationship between privileges within the RBAC system and pairs of levels and compartments within the MLS system. The advantages provided by RBAC, that is, reducing the overall number of connections that must be maintained, and, for example, greatly simplifying the process required in response to a change of job status of individuals within an organization, are then realized without loss of the security provided by MLS.A trusted interface function is developed to ensure that the RBAC rules permitting individuals access to objects are followed rigorously, and provides a proper mapping of the roles to corresponding pairs of levels and compartments. No other modifications are necessary. Access requests from subjects are mapped by the interface function to pairs of levels and compartments, after which access is controlled entirely by the rules of the MLS system.