Controversy has arisen over interpretation of performance validity tests (PVTs) when multiple PVTs are given. Some papers state that more stringent criteria are needed to judge overall performance as invalid, while others argue that concerns about the number of PVTs are overstated and that widely used criteria are appropriate. We examine theoretical models and assumptions, and analyze published data to determine the magnitude of effects implied by theory and observed in practice. Assertions advanced in the primary papers are examined for consistency with the empirical data. Existing theoretical models do not account well for the diverse empirical data, substantial empirical effects remain poorly understood, and the primary papers include assertions that are not empirically supported. The results indicate that: (a) neuropsychology lacks solid theoretical bases for estimating PVT failure rates given various combinations of PVTs, and thus needs to rely on empirical data; (b) existing empirical data fail to support the application of any uniform criteria across the broad range of scenarios involving multiple PVTs; and (c) practice should rely on empirical studies involving combinations of PVTs that have been studied together, in samples clearly appropriate to the individual case, using experimental designs germane to the questions under consideration.