BACKGROUND: Literature on health and access to care of undocumented migrants in the European Union (EU) is limited and heterogeneous in focus and quality. Authors conducted a scoping review to identify the extent, nature and distribution of existing primary research (1990-2012), thus clarifying what is known, key gaps, and potential next steps. METHODS: Authors used Arksey and O'Malley's six-stage scoping framework, with Levac, Colquhoun and O'Brien's revisions, to review identified sources. Findings were summarized thematically: (i) physical, mental and social health issues, (ii) access and barriers to care, (iii) vulnerable groups and (iv) policy and rights. RESULTS: Fifty-four sources were included of 598 identified, with 93% (50/54) published during 2005-2012. EU member states from Eastern Europe were under-represented, particularly in single-country studies. Most study designs (52%) were qualitative. Sampling descriptions were generally poor, and sampling purposeful, with only four studies using any randomization. Demographic descriptions were far from uniform and only two studies focused on undocumented children and youth. Most (80%) included findings on health-care access, with obstacles reported at primary, secondary and tertiary levels. Major access barriers included fear, lack of awareness of rights, socioeconomics. Mental disorders appeared widespread, while obstetric needs and injuries were key reasons for seeking care. Pregnant women, children and detainees appeared most vulnerable. While EU policy supports health-care access for undocumented migrants, practices remain haphazard, with studies reporting differing interpretation and implementation of rights at regional, institutional and individual levels. CONCLUSIONS: This scoping review is an initial attempt to describe available primary evidence on health and access to care for undocumented migrants in the European Union. It underlines the need for more and better-quality research, increased co-operation between gatekeepers, providers, researchers and policy makers, and reduced ambiguities in health-care rights and obligations for undocumented migrants.