This article reports on a programme in which peer-assisted learning (PAL) was combined with case-based learning (CBL) in a second-year radiologic biology unit of study. Our aim is to explore evidence of whether PAL supported the development of qualitative conceptions of learning. The programme involved students in small PAL groups preparing and offering a tutorial based on a case study for the class (large PAL group). The small PAL group assessed the learning of the large PAL group, while the large group gave feedback to the small group. Small groups attended a debriefing session following the tutorial. A six-category framework related to conceptions of learning was developed to guide qualitative analysis of data derived from a student questionnaire, the debriefing sessions and a final focus group. Data analysis indicated some evidence of quantitative conceptions of learning (particularly early in the programme), and showed that PAL played a role in developing students' qualitative conceptions of learning, particularly through the social and affective processes involved and opportunities for developing metacognitive knowledge. The programme contributed to "deep" processing as students learnt from and with each other. Concurrently, students' feelings of responsibility to their peers increased their responsibility for their own learning. The PAL approach that was used provides a basis for further exploration of the role of peers in developing students' conceptions of learning.