The rapid advances in biomedical sciences have induced special moral and ethical attitudes, which ought to be taken into account. One of the most essential issues is the principles for participation in research of subjects with reduced decision-making capacity. We conducted a questionnaire survey among members of the research ethics committees in Sweden to find out their attitudes to a range of ethical issues related to research on subjects with Alzheimer's disease. One hundred thirty-six of those approached responded (66%), and 117 of the responses (56%) were considered substantially complete. There were 16 questions with fixed reply alternatives. Some central questions concerned the informed consent process. With a few exceptions, there were no significant differences in attitudes between the experts and laypersons, between persons of different ages, and between men and women. However, women and laypersons were in general keener to preserve the patient's integrity and the experts were more willing than the laypersons to allow participation of subjects with dementia in placebo-controlled trials.