BACKGROUND The great variety of portfolio types and schemes used in the education of health professionals is reflected in the extensive and diverse educational literature relating to portfolio use. We have recently completed a Best Evidence Medical Education (BEME) systematic review of the literature relating to the use of portfolios in the undergraduate setting that offers clinical teachers insights into both their effects on learning and issues to consider in portfolio implementation. METHODS Using a methodology based on BEME recommendations, we searched the literature relating to a range of health professions, identifying evidence for the effects of portfolios on undergraduate student learning, and assessing the methodological quality of each study. RESULTS The higher quality studies in our review report that, when implemented appropriately, portfolios can improve students' ability to integrate theory with practice, can encourage their self-awareness and reflection, and can offer support for students facing difficult emotional situations. Portfolios can also enhance student-tutor relationships and prepare students for the rigours of postgraduate training. However, the time required to complete a portfolio may detract from students' clinical learning. An analysis of methodological quality against year of publication suggests that, across a range of health professions, the quality of the literature relating to the educational effects of portfolios is improving. However, further work is still required to build the evidence base for the educational effects of portfolios, particularly comparative studies that assess effects on learning directly. DISCUSSION Our findings have implications for the design and implementation of portfolios in the undergraduate setting.