Objective: In problem-based learning curricula, cases are usually clustered into identified themes or organ systems. While this method of aggregating cases presents clear advantages in terms of resource alignment and student focus, an alternative "hidden cluster" approach provides rich opportunities for content integration. Method: The author describes such a model, with report on the extent of integration of behavioral science content across all cases. Results: First-, second- and third-year students were shown to have no significant difference in the percentage of behavioral science learning issues they generated. Conclusion: Due to the growing need to integrate behavioral science concepts into all areas of medical education, a better understanding of programs' successes in this area seems warranted.