The purpose of this study was to explore the relationships among medical students' assessments on peers' group presentations, instructors' assessments of those presentations, and students' educational achievements in other assignments and tests. A total of 101 first-year students from a medical school participated in the study. The students' educational achievements in a 4-week long integrated curriculum were analyzed. Student's final grades were comprised of the following education criteria: two written tests (60%), 15 group reports (25%), one individual report (7%), and four group presentations (15%). We compared scores of the group presentation assessed by the peers and the two instructors. Furthermore, we compared peers' assessment scores with each component of the evaluation criteria. Pearson correlation analysis showed significant correlaton for the assessments between peers and instructors (r=0.775, p<0.001). Peer assessment scores also correlated significantly with scores for the group assignments (r=0.777, p<0.001), final grades on the curriculum (r=0.345, p<0.001), and scores for individual assignments (r=0.334, p<0.001); however, no significant correlation was observed between the peer-assessed group presentation scores and the two written test scores. Peer assessments may be a reliable and valid method for evaluating medical students' performances in an integrated curriculum, especially if the assessments are used to academic processes, such as presentations, with explicit evaluation and judgment criteria. Peer assessments on group presentations might assess different learning domains compared to written tests that primarily evaluate limited medical knowledge and clinical reasoning.