Open-ended tasks were used to examine gender differences in complex mathematical problem solving. The results of this study suggest that, overall, males perform better than females, but the gender differences vary from task to task. A qualitative analysis of student responses to those tasks with gender differences showed that male and female students exhibited many similarities in their solution processes, such as making similar types of mathematical errors and using similar strategies and representations. This study suggests not only the complexity of the issue of gender differences, but also the feasibility and usefulness of using open-ended tasks to explore the issue. Contains 13 references. (Author/MKR)