Decisions by industry sponsors to end clinical trials early for commercial reasons have been the subject of controversy. I argue that the principal consideration in assessing these decisions ought to be the way in which the termination would affect the trial's risk-benefit relationship. If there is not yet sufficient benefit to be gained from the study to offset the risks to which participants were exposed and it is expected that important scientific information would be obtained if the trial were continued, early termination constitutes an unethical alteration of the risk-benefit relationship. This violates the grounds on which permission is given to conduct human research, patients consent to participate, and investigators agree to conduct studies. These knowable and avoidable changes in risk-benefit relationship should generally be seen as impermissible.