Background: In order to gain experience of the skills required when they begin practice, all final-year medical students in the UK undertake a 'student assistantship', working alongside first-year postgraduate doctors. In this study, we examined the learning opportunities open to students in one locality during two periods of assistantship: one in medicine; one in surgery., Methods: Final-year students and their supervisors completed online questionnaires. The students' questionnaire explored general perceptions of the placement, and whether 15 potential learning opportunities (identified as 'desk-' or 'patient-oriented') had been 'taken', 'missed' or were 'not available'. The supervisors' questionnaire explored their perceptions of students' learning during the assistantship., Results: Overall, 86 student questionnaires and 17 supervisor questionnaires were returned (response rates of 57 and 63%, respectively). Students reported more desk-based learning opportunities, of which more were taken up, than patient-oriented learning opportunities. Surgical placements were associated with more 'missed' opportunities than medical placements. Across all tasks, many students felt that some learning opportunities were not present in their assistantship. By contrast, supervisors felt students 'made the most' of assistantships. Students' overall perceptions of the assistantship were positively related to the level of experience that they had attained (r = 0.40-0.54)., Discussion: The assistantship fulfils its aims for many students, but individual experience gained varies considerably. Some opportunities are not being taken, with 'patient-oriented' opportunities more likely to be missed, whereas others are not available during placements. Supervisors may overestimate the educational value of the assistantship, with implications for its management and delivery., (© 2015 John Wiley & Sons Ltd.)