Little is known about medical students' perceptions of the factors that influence their academic performance. To detect factors medical students, in the final years of their undergraduate medical studies, believe affect their academic performance. We conducted semi-structured interviews with high-achieving and re-sitting students in the final two years of their studies in a London medical school. Interviews were recorded and transcribed. Thematic content analysis was conducted. Similarities and differences in factors perceived to affect the academic performance of high-achieving and re-sitting students were identified. Eight re-sitting and ten high-achieving students were interviewed. Three core themes were identified: engagement with learning; reflections on learning methods and experiences and the application of learning to future practice. High-achieving students showed a greater awareness of what worked in terms of their approaches to learning and coping with difficulty than re-sitting students. There were also differences in the degree of positive engagement with peers, suggesting the positive contribution of socialising with other medical students. This exploratory qualitative study identified attitudes, behaviours and motivations that appeared to contribute to success or failure at medical school. Our findings suggest ways to improve appraisal, remediation and support mechanisms for students.