Modeling and simulation (M&S) has tremendous application in private and governmental sectors. From simple to complex constructive simulations, through object-oriented and agent-based simulations, all the way to the large complex distributed simulation environments, M&S affords the opportunity to examine just about anything of interest to the decision maker. We are pleased to present this combined special issue that provides works comprising this full range of M&S applications. Distributed environments composed of live, virtual and constructive (LVC) simulations have been used by the training and experimentation communities for over 10 years. The use of LVC simulation environments is being increasingly examined for potential analytical use, particularly in test and evaluation. The use of LVC for test and evaluation can increase the density and diversity of represented assets, which improves the robustness of the test. The integration of both real and simulated entities, often represented by different levels of realism and fidelity into a common synthetic battlespace or world, presents unique and interesting research challenges for both the analyst attempting to leverage this capability and secondly by the simulation architect attempting to produce credible data from a potentially complex distributed real-time software system. The analyst is often challenged with practical experimental design issues including a limited set of runs (i.e. small sample sizes) due to, for example, limited availability of pilots and operators for the live and virtual assets (i.e. the human subjects) and potential issues with unwanted noise and/or variance being introduced by including too much realism. The simulation architect is challenged with fundamental data consistency issues that arise when the desire to execute in real-time conflicts with the desire to interconnect geographically separated simulations. Additional cross-cutting challenges arise when the desire to reuse existing models and simulations often designed for different purposes are interconnected within the same simulated environment: from the analyst’s perspective of ‘‘will this affect the environment?’’ to the simulation engineer’s perspective of ‘‘are the models interoperable?’’. The first article by Hodson and Hill examines issues associated with using LVC simulation for testing purposes. Largely used in experimental and demonstration purposes, the promise of LVC simulation for test and evaluation purposes does not come without challenges, which are discussed in this lead article. The second article, ‘‘Effectiveness testing of non-lethal weapons’’ by Mezzacappa, argues that LVC simulation provides a crucial component of any research program on non-lethal weapons. The assessment of non-lethal weapons is problematic: it is hard to put humans in harm’s way. This paper discusses the US Army approach to non-lethal weapon assessment and the incorporation of LVC simulation into that testing. The third article, ‘‘Relational oriented systems engineering framework for flight training’’ by Dickerson and Holden addresses complex systems engineering concerns required to realize an LVC simulation for flight training experimentation. The authors introduce a Relational Oriented Systems Engineering (ROSE) methodology for the integration of systems within a system to realize a requisite LVC environment for complex system problems.