A series of computer simulations was run to measure the relationship between testlet validity and the factors of item pool size and testlet length for both adaptive and linearly constructed testlets. Results confirmed the generality of earlier empirical findings of H. Wainer and others (1991) that making a testlet adaptive yields only marginal increases in aggregate validity because of the peakedness of the typical proficiency distribution. Findings suggest that if a linear test is constructed from a much larger calibrated item pool, it can compare quite favorably to an adaptive test. The larger the selection of items from which the test is built, the better the final result. (Contains one figure, four tables, and seven references.) (Author/SLD)