The use of a placebo arm in clinical trials is unethical if there is an active comparator that is acceptably safe and effective. We argue that reasonable evidence of effectiveness and safety of an inexpensive alternative to an expensive therapy is sufficient to require that the inexpensive therapy be included as a comparator when the expensive therapy is tested, and that use of an inactive placebo comparator only is not ethical. For example, studies of the expensive drug eplerenone for congestive heart failure have not included a spironolactone arm, although there is reasonable evidence that spironolactone would be safe and effective, and spironolactone is inexpensive. The requirement to study inexpensive therapies is based on avoidance of unnecessary cost in medical care as an example of non-maleficence. Several ethical actors in the design, conduct, and publication of clinical trials and their results bear responsibility for the appropriate conduct of clinical trials. That responsibility includes protecting study subjects from being asked to participate in clinical trials that serve primarily to promote the use of new and expensive therapies.