International Network for Economic Method Session. Validation is defined as the assessment of the ability of a particular epistemic tool in providing a correct answer to a particular question. Epistemic tools in economics include various types of models and experiments. While for the validation of econometric models there exists a substantial literature, a systematic discussion of the validation of simulations and agent-based models is still lacking. Similarly, there exists a rich literature on internal validity of experiments, but discussions on a systematic approach towards external validity are sparse. In practice, a multitude of strategies, techniques and methods are used to establish validity. A discussion on how these accounts overlap and differ could contribute to a more general validation methodology. A more general validation methodology leads to a more fundamental understanding of science in practice. The purpose of this session is to bring methodological studies of different epistemic tools together to discuss these differences and similarities among the various validation strategies. The papers to be presented are in line with this purpose. The first three focus, respectively, on validating macroeconomic models, economic experiments, and agent-based models. Building on this, the fourth paper will present a more general framework of validation in economics.