在医疗侵权损害赔偿领域，对患者存活或治愈机会丧失的损害赔偿问题，在美国、日本、台湾等地侵权法上已有广泛讨论，但我国立法却没有相关规定。但这一问题不仅关系着对患者生命权和健康权的保护，也涉及到如何在患者和医生间合理分配损害的问题。在患者罹患存活率较低疾病的案件中，医生的过失导致患者病情恶化甚至出现死亡。根据传统的因果关系理论，医疗机构很容易免责，但这对患者来说是不公平的。为了保护患者的正当权益，机会丧失理论产生了。该理论首先是由美国学者Joseph King教授完整提出来的。其内容主要是：如果原告获得更有利结果的机会因为被告的侵权行为而被破坏或减少，那么就丧失的机会，原告可以请求被告予以赔偿。在美国，机会丧失理论是法院审理医疗过失案件时经常运用的一种因果关系理论。在日本，以机会丧失理论为基础的期待权侵害理论在损害赔偿法中占有重要地位。在我国台湾地区，将患者的存活机会纳入人格权之范畴给予保护已经得到了越来越多学者的认同并被应用于审判实践中。机会丧失理论作为一个在理论界尚存争议的学说，在实际运用中尚存在很多困难，重点表现在损害的认定上、因果关系的判断上、损害赔偿数额的计算上。在损害认定上，主要有以存活或治愈机会丧失本身作为损害、以受害人最终的伤残或死亡结果作为损害、以存活或治愈机会丧失引起的损害作为损害三种不同的观点。在因果关系判断上，有必要条件理论、实质要素理论、比例因果关系理论、机会丧失理论等几种不同的学说。在损害赔偿额的计算上，有全部赔偿、比例赔偿、法官自由裁量等几种不同的方法。由于机会不易量化，这决定了机会丧失理论适用时要有所限制，否则将很容易造成不确定性的扩张，导致滥诉情况的出现，增加诉讼成本。因此，在适用时，笔者认为应当注意：实际损害尚未发生时不适用、单纯由于医疗过失导致的损害不适用、超过百分之五十的机会损害时不适用、建立在受害人假想损害之上的机会不适用。在我国，由于对机会丧失的损害赔偿无法律的明文规定，在遇到此类案件时，法院往往依据公平责任原则，判令医疗机构向患者支付一定的赔偿费用。然而公平责任原则是适用于当事人双方均无过错的情况下的，在机会丧失的案件中，被告医生的过失显而易见，因此，这样判决虽然维护了实质正义，却违反了立法规定，有损法律的权威。因此，虽然当前对该理论是否应当立法，理论界尚存很大争议，但笔者认为，在我国当前法律体系中是存在该理论的立法空间的，而且应当在法律中对其予以规定来更好的保护患者的利益和维护法律的权威。

In the area of medical malpractice, the issue of damages for loss of chance of survival or cure has been broadly discussed in the United States, Japan and Taiwan. In China, however, there is no concerned specific law and regulation. But it not only relates to the protection of patient’s rights of life and health, but also relates to the proper allocation of loss between patients and medical practitioners.In the case that the patient suffers from lower survival rate disease, the doctor’s fault causes the deterioration or even death. According to the traditional causality theory, medical institutions can easily shirk the responsibility, but it is unfair to the patient. In order to protect the legitimate rights of the patient, the loss-of-a-chance doctrine comes out. This doctrine is first brought out by American scholar Professor Joseph King. The main content of this doctrine is: If the infringement of the defendant destroys or reduces the chance for the plaintiff to get more favorable results, then the plaintiff may request compensation for the lost opportunity.In the United States, the loss-of-a-chance doctrine is a causality theory which is usually used to deal with the cases of medical malpractice. In Japan, the expectant right infringement theory, which is based on the loss-of-a-chance doctrine, plays an importance role in the compensation law. In Taiwan, the survival chance is protected as personality right, which is agreed by more and more scholars and applied in the trial practice.As a still controversial theory, there are many difficulties for the loss-of-a-chance doctrine to be used in practice. It mainly reflects in such aspects as follows: the identification of the damage, the judgement of the causality, the calculation of the compensation. In the identification of the damage, there are three different opinions: take the loss of the chance as the damage, take the final results as the damage, take the damage caused by the loss of chance as the damage. In the judgement of the causality, there are some different theories: the essential condition theory, the substantial element theory, the scale causality theory, the loss-of-a-chance theory. In the calculation of the compensation, there are some different methods, such as full compensation, scale compensation, free discretion by the judge.Since chance can not be easily quantified, the loss-of-a-chance doctrine can not be used without limitation. Otherwise, it can easily result to the expansion of the uncertainty, then lead to the emergence of the abuse and increase the cost. So, when it puts into use, the author thinks that it must have some limitations. It is not applicable when the actual damage has not happened, when the damage comes out only because of the medical negligence, when the chance of the damage is more than 50 percent, when the damage of the chance based on the supposition of the victim.In China, since there is no express term in our compensation law, when this kind of thing happens, the court often order the medical institution to pay the patient on the basis of fair liability principle. However, the fair liability principle is only applied in the situation that both parties have no fault. In the case of loss-of-a-chance, it is obvious that the doctor has fault, so the decision maintains the substantial justice, but violates the legislation and breaks the law. Although there are many different opinions, the author still agrees that it is necessary to bring this doctrine into our law to provide better protection of the patients and maintain the majesty of the law, and there is legislation space for this doctrine in our current legal system.