A study was conducted to compare tailored testing procedures based on a Bayesian ability estimation technique and on a maximum likelihood ability estimation technique. The Bayesian tailored testing procedure selected items so as to minimize the posterior variance of the ability estimate distribution, while the maximum likelihood tailored testing procedure selected items so as to maximize the item information for the current ability estimate. Results of the analyses for the two procedures indicated that the optimal test length of Bayesian procedure was 14 items, while the optimal test length of the maximum likelihood procedure was 12 items. No difference was found between the procedures in terms of the reliability of the ability estimates. The Bayesian procedure yielded greater mean total test information than the maximum likelihood. The goodness of fit comparison indicated that the Bayesian procedure yielded poorer fit of the 3PL model to the data than did the maximum likelihood procedure. It was concluded that for large scale tailored testing, a maximum likelihood tailored testing procedure with item selection based on information is the procedure of choice. (Author/GK)