Salway et al. BMC Public Health 2011, 11:514 http://www.biomedcentral.com/1471-2458/11/514 Background Public health researchers are increasingly encouraged to establish international collaborations and undertake cross-national comparative studies. Funding streams such as the European Commission’s Framework pro- grammes explicitly require such research designs, while others strongly encourage this approach. Recent invest- ments in the production of harmonized datasets (such as EURO-PERISTAT, [1] and EUROTHINE [2]) and the fielding of international surveys (such as the European Social Survey [3]) also encourage researchers to under- take cross-national research, as do individual and orga- nisational assessments of research quality (such as the Research Excellence Framework in the UK) that reward international partnerships. The field of migration and ethnic diversity might reason- ably be considered an obvious domain for such cross- national comparative research. The majority of high income countries have experienced significant levels of immigration (both planned and enforced) in recent dec- ades with consequent increased ethno-cultural diversity. There is considerable variation, both within and across countries, in how these processes have been problematised and responded to, with divergent opinions expressed as to: the nature of the ‘problem’; the goals of integration; appro- priate relationships between migrants and their new coun- try; and the obligations of government and wider society to newcomers [4]. There would therefore seem to be great potential for mutual learning and joint problem-solving through collaborative and comparative research in relation to migration and ethnicity. Indeed, a number of important comparative studies focusing on immigration, integration, cohesion, discrimination, (in)equality and related issues have been published in recent years [5,6]. It is perhaps sur- prising therefore that there has to-date been relatively little cross-national comparative work within the field of ethni- city and health. For instance, our review of the 10 issues of Ethnicity & Health including and preceding volume 15(4) published in 2010 revealed that none of the 58 papers published included any such international comparative dimension. Similarly, the 10 most recent issues of Interna- tional Journal of Migration, Health & Social Care dating back from volume 6(1) published in 2010, included just four papers with an international comparative focus out of 43 original articles. Further, where such research has been undertaken it has tended to focus on recent immigrants, rather than more established minorities. One factor that might discourage public health researchers from taking an international comparative design is the subscription to differentialist conceptualisa- tions of ethnicity. Recent years have witnessed some- thing of a backlash against earlier health-related research which tended to portray ethnic group identities as natural and fixed and to seek explanations for health Page 2 of 13 disadvantage largely in genetic or cultural factors [7-9]. Understandings of ethnic identity that foreground its contingent, contested and fluid nature may sit uneasily with cross-national comparative research. Studies that seek to compare the experiences and outcomes of migrant/minority groups across national settings might be seen to at best offer little in the way of analytical purchase and at worst to privilege genetic or culturalist accounts (since they might implicitly assume an ethnic ‘essence’ that exists irrespective of time or place). However, recent work has argued that comparative research can be useful precisely because there is a need to take social context seriously and it allows an explora- tion of how the significance of ethnic identities varies over time and place [10]. We further suggest that such work can offer other advantages in relation to research that engages with issues of ethnicity, migration and health. Comparative analyses offer the potential for new insights into how the wider socio-political context impacts upon experiences and outcomes of healthcare. More generally, comparative studies provide an ideal opportunity to set aside routine approaches to addres- sing problems and to engage in critical analyses of cur- rent policy and practice [11,12]. Comparative analyses can potentially: highlight the competing priorities oper- ating in different contexts; make visible taken-for- granted assumptions and underlying ideologies; reveal the arbitrariness of particular categorisations and con- cepts; and suggest innovative solutions. Nevertheless, studies that include more than one national context and involve researchers based at disparate institutions operating within contrasting academic envir- onments imply significant additional conceptual, metho- dological and logistical complexity, as well as increased costs, when compared to national studies. Bhopal [13] identifies several factors that can hamper cross-national comparative research on ethnicity and health, including: differing migration histories and policy contexts; differ- ences in the use of ethnic categories and in routine data collection; and divergent perspectives regarding the desir- ability and need for such research. It is also clear, however, that divergent approaches to undertaking comparative research are emerging in the field of migration, ethnicity and health, raising fundamental questions about how and why such research should be undertaken. Yet, unlike other fields [14,15] public health researchers have not to-date given considered attention to the opportunities and chal- lenges that cross-national comparative studies offer to the field of migration, ethnicity and health. Given the likely growth in such comparative research, we suggest that it is important to debate the value of this work and to seek to identify key issues for reflection. The present paper contri- butes by drawing on the insights and findings of a recent preliminary study focused on maternal health.