The United States Department of Defense's High Level Architecture for Modeling and Simulation (HLA) provides a standardized interface for distributed simulations. The recent advent of HLA has greatly increased interest in the use of distributed, interoperable simulation model components. To date, most models using HLA have been developed in conventional high-level languages (primarily C++). This paper presents approaches by which HLA can be used to interconnect distributed model components which are developed using commercially available, off-theshelf simulation software. The requirements imposed on such simulation software by HLA are discussed, and four approaches for adapting such software for use with HLA are presented. A generalized, model-independent approach which was developed for SLX is presented.