This report presents four tests for evaluating any zero-dimensional reservoir model. Using these tests, the general validity of the reservoir per se (RPS) and the standard zero-dimensional (SZD) gas reservoir models was determined. Neither model is generally valid as that term is herein defined. However, both models passed the reservoir-pressure lifetime history matching test for the Katy V-C and Chattian Main Sand gas reservoirs. Although the RPS model does poorly in estimating reservoir parameters from history matching when the match extends over the entire lifetime of the reservoir, it is better than the SZD model at predicting future reservoir pressures. The equations of the two models are described in detail, and the results of the individual tests are reported. 23 references, 17 figures, 4 tables.