The article provides an analysis used abroad to solve problems associated with the complicated causality theory. It has come to be known as the «lost of chance doctrine» and is one of the cases of complicated cause. In the Russian legal order, the first scientific publications on the topic have only recently begun to appear, isolated glimpses of its use have begun to arise in court practice. In general, an effective theory is considered to be applicable to a situation where both the defendant's action and the risk penetrating the victim's own control can equally possibly act as a possible cause of the occurrence of harm. Moreover, the reason for this uncertainty is the limited possibilities of human cognition, since it is not objectively possible to determine whether the victim would have realized his chance if he had not been deprived of it or not. The compensation awarded to the victim in this case is calculated in proportion to the quantitative reduction of chances.

It seems extremely useful to consider the potential application of this theory in our legal order based on the study of international experience in its use.

The study used the dialectical method of cognition, as well as linguistic and comparative legal research methods.

In this article it have been demonstrated how various legal systems relate to the doctrine of loss of chance and in what form it is reflected in judicial practice. So, in some legal systems, the theory is recognized and actively applied by the courts (France, USA, Great Britain), since it is believed that only with its help it is possible to fairly resolve situations in the development of which chances interfere. While other legal systems strongly reject the theory (Germany, Austria, Switzerland), trying to find solutions within the framework of traditional views on causalities in law.