One important and promising application of item response theory (IRT) is computerized adaptive testing (CAT). The implementation of a nominal response model-based CAT (NRCAT) was studied. Item pool characteristics for the NRCAT as well as the comparative performance of the NRCAT and a CAT based on the three-parameter logistic (3PL) model were examined. Ability estimates were generated at test lengths of 10, 15, 20, 25, and 30 items from item pools of 90 items. Abilities were generated for 1,300 examinees in 1 study and for 900 examinees in the other study. Results show that for 2-, 3-, and 4-category items, items with maximum information of at least 0.16 produced reasonably accurate ability estimation for tests with a minimum test length of about 15 to 20 items. Moreover, the NRCAT was able to produce ability estimates comparable to those of the 3PL CAT. Implications of these results were discussed. Eight tables and six graphs illustrate the discussion. (SLD)