This paper discusses the findings of a pilot project exploring the benefits and costs of social work student placements to host agencies. In this qualitative study, 43 supervisors were interviewed about their experiences of the costs and benefits of having a student on placement. Overall, the benefits were assessed as outweighing the costs. The main benefit identified was the work undertaken by students, such as counselling, research projects, evaluations, group work and staff training. Importantly, enhancement of the supervisors' own professional development and reflection on practice was the second most frequently identified benefit. An unanticipated benefit was that placements appear to function as pre-employment trials, with 60% of respondents reporting that students were subsequently employed by the practicum agency. The major costs included time spent in student supervision and student use of agency resources.