Jehovah's Witnesses' (JWs) refusal of blood transfusions has recently gained support in the medical community because of the growing popularity of "no-blood" treatment. Many physicians, particularly so-called "sympathetic doctors", are establishing a close relationship with this religious organization. On the other hand, it is little known that this blood doctrine is being strongly criticized by reform-minded current and former_JWs who have expressed conscientious dissentfrom the organization. Their arguments reveal religious practices that conflict with many physicians' moral standards. They also suggest that a certain segment of "regular" or orthodox J7Ws may have different attitudes towards the blood doctrine. The author considers these viewpoints and argues that there are ethicalflaws in the blood doctrine, and that the medical community should reconsider its supportive position. The usual physician assumption that JWs are acting autonomously and uniformly in refusing blood is seriously questioned.(J7ournal ofMedical Ethics 1998;24:223-230)