The advantages of administering an adaptive test battery, a collection of multiple adaptive subtests that are specifically tailored to examinees’ abilities, include shortening the subtest length and maintaining the accuracy of individual subtest scores. The test battery can incorporate a range of subjects, though this study focused primarily on Math and Reading. This study compared different ways of incorporating collateral information (CI), supplementary information beyond examinees’ current test performance, under two frameworks (Unidimensional and Multidimensional computerized adaptive testing). It also investigated the impact of subtest intercorrelations (the relationship between an examinee’s test scores), as well as the sequences of subtest administration on ability estimation in a variable-length adaptive battery. Practical issues including content constraints and item exposure control were also considered. Findings showed that the CI methods improved measurement efficiency with an acceptable level of measurement precision. The CI was more beneficial when associated with higher intercorrelations among the subtests. Also, the CI was found to be advantageous during the early stages of the subtests which were not taken first. Therefore, the CI may improve the examinee experience by administering items more aligned with their abilities. In addition, the CI should reduce costs for testing organizations by requiring fewer items and possibly saving seat time, while still providing reliable scores. The results should help practitioners decide whether the use of the CI is worthwhile under their particular testing situation.