The aim of the present research was to develop a computer adaptive test with the graded response model to measure the Five Factor Model of personality attributes. In the first of three studies, simulated items and simulated examinees were used to investigate systematically the impact of several variables on the accuracy and efficiency of a computer adaptive test. Item test banks containing more items, items with greater trait discrimination, and more response options resulted in increased accuracy and efficiency of the computer adaptive test. It was also found that large stopping rule values required fewer items before stopping but had less accuracy compared to smaller stopping rule values. This demonstrated a trade-off between accuracy and efficiency such that greater measurement accuracy can be obtained at a cost of decreased test efficiency. In the second study, the archival responses of 501 participants to five 30-item test banks measuring the Five Factor Model of personality were utilized in simulations of a computer adaptive personality test. The computer adaptive test estimates of participant trait scores were highly correlated with the item response theory trait estimates, and the magnitude of the correlation was related directly to the stopping rule value with higher correlations and less measurement error being associated with smaller stopping rule values. It was also noted that the performance of the computer adaptive test was dependent on the personality factor being measured whereby Conscientiousness required the most number of items to be administered and Neuroticism required the least. The results confirmed that a simulated computer adaptive test using archival personality data could accurately and efficiently attain trait estimates. In the third study, 276 student participants selected response options with a click of a mouse in a computer adaptive personality test (CAPT) measuring the Big Five factors of the Five Factor Model of personality structure. Participant responses to alternative measures of the Big Five were also collected using conventional paper-and-pencil personality questionnaires. It was found that the CAPT obtained trait estimates that were very accurate even with very few administered items. Similarly, the CAPT trait estimates demonstrated moderate to high concurrent validity with the alternative Big Five measures, and the strength of the estimates varied as a result of the similarity of the personality items and assessment methodology. It was also found that the computer adaptive test was accurately able to detect, with relatively few items, the relations between the measured personality traits and several socially interesting variables such as smoking behavior, alcohol consumption rating, and number of dates per month. Implications of the results of this research are discussed in terms of the utility of computer adaptive testing of personality characteristics. As well, methodological limitations of the studies are noted and directions for future research are considered. (PsycINFO Database Record (c) 2004 APA, all rights reserved).