BACKGROUND: Case-based learning (CBL) is a long established pedagogical method, which is defined in a number of ways depending on the discipline and type of 'case' employed. In health professional education, learning activities are commonly based on patient cases. Basic, social and clinical sciences are studied in relation to the case, are integrated with clinical presentations and conditions (including health and ill-health) and student learning is, therefore, associated with real-life situations. Although many claims are made for CBL as an effective learning and teaching method, very little evidence is quoted or generated to support these claims. We frame this review from the perspective of CBL as a type of inquiry-based learning. AIM: To explore, analyse and synthesise the evidence relating to the effectiveness of CBL as a means of achieving defined learning outcomes in health professional prequalification training programmes. METHOD: SELECTION CRITERIA: We focused the review on CBL for prequalification health professional programmes including medicine, dentistry, veterinary science, nursing and midwifery, social care and the allied health professions (physiotherapy, occupational therapy, etc.). Papers were required to have outcome data on effectiveness. SEARCH STRATEGIES: The search covered the period from 1965 to week 4 September 2010 and the following databases: ASSIA, CINAHL, EMBASE, Education Research, Medline and Web of Knowledge (WoK). Two members of the topic review group (TRG) independently reviewed the 173 abstracts retrieved from Medline and compared findings. As there was good agreement on inclusion, one went onto review the WoK and ASSIA EndNote databases and the other the Embase, CINAHL and Education Research databases to decide on papers to submit for coding. Coding and data analysis: The TRG modified the standard best evidence medical education coding sheet to fit our research questions and assessed each paper for quality. After a preliminary reliability exercise, each full paper was read and graded by one reviewer with the papers scoring 3-5 (of 5) for strength of findings being read by a second reviewer. A summary of each completed coding form was entered into an Excel spread sheet. The type of data in the papers was not amenable to traditional meta-analysis because of the variability in interventions, information given, student numbers (and lack of) and timings. We, therefore, adopted a narrative synthesis method to compare, contrast, synthesise and interpret the data, working within a framework of inquiry-based learning. RESULTS: The final number of coded papers for inclusion was 104. The TRG agreed that 23 papers would be classified as of higher quality and significance (22%). There was a wide diversity in the type, timing, number and length of exposure to cases and how cases were defined. Medicine was the most commonly included profession. Numbers of students taking part in CBL varied from below 50 to over 1000. The shortest interventions were two hours, and one case, whereas the longest was CBL through a whole year. Group sizes ranged from students working alone to over 30, with the majority between 2 and 15 students per group. The majority of studies involved single cohorts of students (61%), with 29% comparing multiple groups, 8% involving different year groups and 2% with historical controls. The outcomes evaluation was either carried out postintervention only (78 papers; 75%), preintervention and postintervention (23 papers; 22%) or during and postintervention (3 papers; <3%). Our analysis provided the basis for discussion of definitions of CBL, methods used and advocated, topics and learning outcomes and whether CBL is effective based on the evaluation data. CONCLUSION: Overwhelmingly, students enjoy CBL and think that it enhances their learning. The empirical data taken as a whole are inconclusive as to the effects on learning compared with other types of activity. Teachers enjoy CBL, partly because it engages, and is perceived to motivate, students. CBL seems to foster learning in small groups though whether this is the case delivery or the group learning effect is unclear.