During the past 10 years, there has been a rapidly growing number of pharmaceutical industry-sponsored drug trials for treatment of Alzheimer disease (AD) and other neurodegenerative diseases. As public awareness and concerns about AD have grown, so has interest in developing drug therapies for retarding symptom progression, delaying onset, and ultimately curing the disease. Ethical debate on the use of placebo control trials in AD research has come of age in the United States with the availability of treatments approved by the Food and Drug Administration. The experts and the public agree that more effective therapies are necessary, and new therapeutic options are being developed as rapidly as possible. The arguments on each side of the debate are provocative and important but do not provide unequivocal justification for either the abandonment or the maintenance of placebo-controlled trials in all AD research. Clinical trials differ with respect to scientific and practical goals, and these factors inherently affect the ethical priorities of each study. We present these contrasting points of view to delineate some of the issues rather than to make specific recommendations other than to urge that all clinical trials in AD should be designed with careful consideration of the ethical issues surrounding the use of placebo controls. As new and more effective treatments emerge, the ethical framework for placebo use in AD studies will require frequent re-examination. To make wise choices, patients, caregivers, physicians, and ethicists (among others) must have a voice in this continuing discussion.