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The present study examined the contributions of various item characteristics to the difficulty of the individual items on the Mental Rotation Test (MRT). Analyses of item difficulties from a large data set of university students were conducted to assess the role of time limitation, distractor type, occlusion, configuration type, and the degree of angular disparity. Results replicated in large part previous findings that indicated that occluded items were significantly more difficult than non-occluded and that mirror items were more difficult than structural items. An item characteristic not previously examined in the literature, configuration type (homogeneous versus heterogeneous), also was found to be associated with item difficulty. Interestingly, no significant association was found between angular disparity and difficulty. Multiple regression analysis revealed that a model consisting of occlusion and configuration type alone was sufficient for explaining 53 percent of the variance in item difficulty. No interaction between these two factors was found. It is suggested, based on overall results, that basic figure perception, identification and comparison, but not necessarily mental rotation, account for much of the variance in item difficulty on the MRT.