Introduction Portfolio-based assessments require that learners' competence development is adequately reflected in portfolio documentation. This study explored how students select and document performance data in their portfolios and how they perceive these data to be representative for their competence development. Methods Students uploaded performance data in a competency-based portfolio. During one clerkship period, twelve students also recorded an audio diary in which they reflected on experiences and feedback that they perceived to be indicants of their competence development. Afterwards, these students were interviewed to explore the extent to which the performance documentation in the portfolio corresponded with what they considered i...