While it is widely agreed that human behavior representations (HBRs) must be validated before they are incorporated into military simulations, there is much less agreement on what activities and evidence satisfy validation requirements. In this paper we will begin by discussing psychological taxonomies of theory and measurement validity, identifying some insights that the Department of Defense Modeling and Simulation community might gain from these well-established paradigms. This discussion will include brief descriptions of a variety of techniques for collecting validity evidence gleaned from the psychological research literature. While qualitative evidence will be mentioned, special emphasis will be placed on quantitative techniques for assessing HBR validity. A number of relevant issues, such as appropriate and inappropriate statistical tests, overfitting data, and model complexity, will be addressed. Next, we will discuss some limitations of the psychological perspective in general and for our community in particular. Finally, we will expand on Defense Modeling and Simulation Office's definition of validity and illustrate how this definition provides guidance for additional HBR assessment measures and processes that are highly appropriate for the military user community.