Introduction: In health science education clinical clerkships serve the twofold purpose of guiding student learning and assessment of performance. Evidently, both formative and summative assessment procedures are needed in clerkship assessment. In-training evaluation (ITE) has the potential to serve both assessment functions. Implementation of effective ITE, however, has been shown to be problematic, partly because integration of assessment functions may have negative consequences for teaching and learning. This study investigates student perceptions of the impact of an integrated assessment approach, seeking to refine criteria for effective ITE. Method: In the curriculum of Maastricht Midwifery School (MMS), clerkship assessment is based on ITE serving both assessment functions. The ITE model is based on principles of extensive work sampling, and frequent documentation of performance. A focus group technique was used to explore student perceptions on the impact of the ITE approach on student learning and supervisor teaching behaviour, and on the usefulness of information for decision making. Results: Results indicate that the assessment approach is effective in guidance of student learning. Furthermore, students consider the frequent performance documentation essential in clerkship grading. Acceptance and effectivity of ITE requires a learning environment which is safe and respectful. Transparency of assessment processes is the key to success. Suggestions for improvement focus on variation in evaluation formats, improvement of feedback (narrative, complete) and student involvement in assessment. Conclusion: ITE can fulfill both its formative and summative purposes when some crucial conditions are taken into account. Careful training of both supervisors and students in the use of ITE for student learning and performance measurement is essential.