Objective: Empathy is a prominent goal of medical education that is too often underachieved. Using concept mapping, the authors constructed a student-generated conceptual model of factors viewed as affecting empathy during medical education. Methods: During the 2005-2006 academic year, 293 medical students and interns answered a brainstorming survey asking respondents to list factors affecting empathy, and 34 participants then sorted the factors into categories and rated each factor's relative importance. Factors and ratings were examined using multidimensional scaling and cluster analyses, Pearson's r, and Student's t test. This process, known as "concept mapping," was conducted using Concept Systems. Results: One hundred sixty perceived empathy factors were identified and sorted into four clusters: personal experiences, connections and beliefs; negative feelings and attitudes toward patients; mentoring and clinical experiences that promote professional growth (rated most important); and school and work experiences that undermine development of empathy (rated least important). All students rated factors in a similar hierarchical fashion across all four clusters with no differences among groups. Listening was the most highly rated factor. Conclusion: Students consider experiences that promote personal and professional growth to be the most important factors affecting empathy in medical education. Though less important to students, negative feelings and attitudes toward patients, as well as negative school and work experiences, affect empathy at all stages of education.