This Article reviews the essential findings of studies of variations in quality of care according to three categories of care: effective care, preference-sensitive care, and supply-sensitive care. It argues that malpractice liability and informed consent laws should be based on standards of practice that are appropriate to each category of care. In the case of effective care, the legal standard should be that virtually all of those in need should receive the treatment, whether or not it is currently customary to provide it. In the case of preference-sensitive care, the law should recognize the failure of the doctrine of informed consent to assure that patient preferences are respected in choice of treatment; we suggest that the law adopt a standard of informed patient choice in which patients are invited, not merely to consent to a recommended treatment, but to choose the treatment that best advances their preferences. In the case of supply-sensitive care, we suggest that physicians who seek to adopt more conservative patterns of practice be protected under the "respectable minority" or "two schools of thought" doctrine.