There is little UK-based empirical research on South Asian participation in clinical trials. The predominantly US literature rarely engages with mainstream debates about ethnicity, diversity and difference. This study was prompted by a lack of knowledge about how South Asian people perceive trial involvement and the risks and benefits involved. Face to face interviews were conducted with 25 health professionals (consultants, GPs, nursing staff, academics, non-medically trained trial co-ordinators, LREC and MREC members) and 60 South Asian lay people (20 Indians, 20 Pakistanis and 20 Bangladeshis) who had not taken part in a trial. The study took place in the Leeds and Bradford areas of England. It was found that lay South Asian attitudes towards clinical trial participation focused on similarities rather than differences with the general UK population, suggesting that the relevance of ethnicity should be kept in perspective. There was no evidence of antipathy amongst South Asians to the concept of clinical trials, and awareness was a correlate of social class, education and younger age. Lay factors that might affect South Asian participation in clinical trials included: age; language, social class; feeling of not belonging/mistrust; culture and religion. Approachable patients (of the same gender, social class and fluent in English) tended to be 'cherry picked' to clinical trials. This practice was justified because of a lack of time, resources and inadequate support. South Asian patients might be systematically excluded from trials due to the increased cost and time associated with their inclusion, particularly in relation to the language barrier. Under-representation might also be due to passive exclusion associated with cultural stereotypes. The paper concludes by applying the theoretical framework of institutional racism as a means of making sense of policy and practice. At the same time, caution is advocated against using ethnicity as the only form of discrimination facing minority ethnic populations.