Background: Clinical workplace-based learning has been the means to becoming a medical professional for many years. The importance of an adequate patient mix, as defined by the number of patients and the types of medical problems, for an optimal learning process is based on educational theory and recognised by national and international accreditation standards. The relationship between patient mix and learning in work-based curricula as yet remains unclear. Aim: To review research addressing the relationship between patient mix and learning in work-based clinical settings. Method: The search was conducted across Medline, Embase, Web of Science, ERIC and the Cochrane Library from the start date of the database to July 2011. Original quantitative studies on the relationship between patient mix and learning for learners at any level of the formal medical training/career were included. Methodological quality was assessed and two reviewers using pre-specified forms extracted results. Results: A total of 10,420 studies were screened on title and abstract. Of these, 298 articles were included for full-text analysis, which resulted in the inclusion of 22 papers. The quality of the included studies, scored with the Medical Education Research Study Quality Instrument (MERSQI), ranged from 8.0 to 14.5 (of 18 points). A positive relationship was found between patient mix and self-reported outcomes evaluating the progress in competence as experienced by the trainee, such as self-confidence and comfort level. Patient mix was also found to correlate positively with self-reported outcomes evaluating the quality of the learning period, such as self-reported learning benefit, experienced effectiveness of the rotation, or the instructional quality. Variables, such as supervision and learning style, might mediate this relationship. A relationship between patient mix and formal assessment has never been demonstrated. Conclusion: Patient mix is positively related to self-reported learning outcome, most evidently the experienced quality of the learning programme.