Medical education has been shown to negatively influence student attitudes toward certain types of patient populations. Past research does not inform current educational practice because today's medical school environment is different from when most of the published research was conducted. There are more female students, curricular innovations such as problem-based learning have changed the framework for educational delivery, and longitudinal studies, which could inform when interventions may be needed, are uncommon. The purposes of this longitudinal, prospective cohort study were to compare the attitudes of Problem-based learning and Traditional curriculum students toward providing care for medically indigent patients as they progressed through the four-year undergraduate medical education curriculum, and to determine if gender differences were apparent and persisted over time. Attitudes of one cohort of students enrolled in separate curricula were studied. The outcome measure was the Medical Student Attitudes Toward the Underserved questionnaire, which was administered three times. A linear mixed effects regression analysis was performed to examine changes in factor scores over time and whether these changes differed between Problem-based and Traditional students, and males and females. Longitudinal findings revealed that commitment to caring for the medically underserved was greater when students entered medical school than when they graduated. Students in both curricula, as well as male and female students, experienced increasingly negative attitudes over the four year period. Decline in attitudes toward medically underserved patients was similar to previous research results. This study showed that attitudes of students were not influenced by the preclinical curriculum they experienced.