Objective There is great interest in conducting clinical trials of disease‐modifying therapies in the prodromal (early, pre‐dementia), asymptomatic stages of Alzheimer's disease. Diagnostic biomarker tests offer a means of identifying prodromal patients, but it is unclear how potential participants feel about their use. Deciding whether to take part in a clinical trial is a complex process in which eligible participants must balance risks and discomforts against uncertain benefits. We sought to explore the views of potential participants through qualitative research methods. Methods Focus groups with people with early memory problems, current and former family carers explored attitudes towards participating in clinical trials in the prodromal stages of the disease, using an example of anti‐amyloid antibody‐therapy (immunotherapy), which are currently in development. Results Despite the complexities involved, almost all participants had a clear idea about whether they, personally, would like to take part. Many were highly motivated to obtain an unambiguous diagnosis, regardless of their desire to participate in a clinical trial. Participants expressed minimal concern regarding the risk of adverse events associated with immunotherapy, whereas certain tests and trial procedures provoked greater anxiety. People with memory problems were found to assess the study demands in relation to their own priorities and circumstances. Conclusions The priorities of patients might be different to clinicians and those who design and regulate clinical trials. Patient views can be used to inform the ethical debate around the disclosure of biomarker status, the design of clinical trials and the content of trial information. Copyright © 2013 John Wiley & Sons, Ltd.