PURPOSE: Computerized adaptive tests (CATs) have efficiency advantages over fixed-length tests of physical functioning but may lose sensitivity when administering extremely low numbers of items. Multidimensional CATs may efficiently improve sensitivity by capitalizing on correlations between functional domains. Using a series of empirical simulations, we assessed the efficiency and sensitivity of multidimensional CATs compared to a longer fixed-length test. METHOD: Parent responses to the Pediatric Evaluation of Disability Inventory before and after intervention for 239 children at a pediatric rehabilitation hospital provided the data for this retrospective study. Reliability, effect size, and standardized response mean were compared between full-length self-care and mobility subscales and simulated multidimensional CATs with stopping rules at 40, 30, 20, and 10 items. RESULTS: Reliability was lowest in the 10-item CAT condition for the self-care (r = 0.85) and mobility (r = 0.79) subscales; all other conditions had high reliabilities (r > 0.94). All multidimensional CAT conditions had equivalent levels of sensitivity compared to the full set condition for both domains. CONCLUSIONS: Multidimensional CATs efficiently retain the sensitivity of longer fixed-length measures even with 5 items per dimension (10-item CAT condition). Measuring physical functioning with multidimensional CATs could enhance sensitivity following intervention while minimizing response burden.