Objectives To compare the motives and experiences of different ethnic groups participating in a randomised double blind placebo-controlled trial of montelukast in preschool wheeze, and to assess parents’ or guardians’ understanding of trial procedures and their implications, including the collection of genetic material.

Design Qualitative interviews with parents or guardians.

Setting Interviews occurred in the homes of London children recruited to a national multicentre clinical trial following primary and secondary care attendance with wheeze.

Participants 42 parents (20 of Bangladeshi origin, 10 white UK, 12 other ethnicities) of preschool children enrolled in a clinical trial.

Results Bangladeshi families were relatively reluctant to participate in the qualitative study, despite strong engagement with the parent study. Anxiety related to wheezing was a common primary motive for trial enrolment. Parents viewed the trial as a route to improved treatment. Verbal delivery of trial information appeared more effective than study literature, especially for Bangladeshi families, with low parental literacy and high levels of trust in medical professionals potential contributors to this effect. All ethnic groups expressed a low understanding and/or retention of essential study concepts such as randomisation and genetic testing.

Conclusions Bangladeshi families are particularly motivated to participate in clinical trials despite variable comprehension of study concepts. This motivation is more strongly contingent on strong researcher-subject rapport than on the quality of study literature. Trial teams seeking to recruit from South Asian populations should emphasise face-to-face verbal explanation of trial concepts and procedures and consider modified trial literature.