The purpose of this study was to investigate the relationship between both 9th-grade and 1st-year undergraduate students' use of "look back" strategies and problem solving performance in multiple solution methods, the difference in their use of look back strategies and problem solving performance in multiple solution methods, and the role of look back strategies in problem solving in multiple solution methods. Data for this study were comprised of 30 9th-grade and 30 1st-year undergraduate students' problem solving scores in multiple solution methods and their think-aloud protocols. Based on and expanded from Polya's (1973) ideas, "look back" in the present study means "examination of what was done or learned previously." The results of this study indicated that both the 9th-grade and 1st-year undergraduate students who looked back more frequently tended to perform better in multiple solution methods, the 1st-year undergraduate students tended to look back more frequently and perform better than the 9th-grade students in multiple solution methods, and both the 9th-grade and 1st-year undergraduate students tended to review and to compare multiple solution methods in their use of look back strategies.