We conducted this study to determine the relationship between math preference and mastery for five middle school students with autism spectrum disorders. We randomly presented several math addition and subtraction problem formats to determine the students' preferences. Results indicated that preference was idiosyncratic across students. In addition, preference was not related to mastery in some students. Results are discussed within a theoretical framework of matching law. Implications for practitioners are discussed. (Contains 5 figures, 2 tables and 1 footnote.)