Background: The accuracy of medical student logbooks has not been extensively studied. Purpose: The purpose of this study was to determine accuracy of student entry of core problems and completeness of patient entry in an electronic logbook. Methods: Third-year internal medicine clerkship students entered patient encounters as required by the clerkship. Experts entered information from the same encounters. Results: A total of 1,440 patient entries generated by 37 consecutive students were compared to expert entries. Sensitivity (core problem underreporting) was low (60%, SD = 22%). Percent agreement (87%, SD = 7%), kappa (0.46, SD = 0.19), and specificity (core problem overreporting; 95%, SD = 5%) were good to excellent. Students both omitted (underreported 14%, SD = 12%) and overreported (23%, sd 17%) patients. Conclusions: Under ideal study circumstances, there was significant underreporting of core problems by students. Although the high specificity, meaning that students are not reporting problems they have not encountered, is reassuring, logbook sensitivity in this study was not good enough for high-stakes evaluations of students or for medical school licensing.