The rules of the division of responsibilities between perpetrators of loss in Islamic law & the legal system of IranProof of liability depends on relating loss to someone who is perpetrators of loss. So establishing this issue is necessary for proving the attribution of the loss to the agent. In the cases that the agent is one person, the verdict is clear because in these cases, proving the attribution of the loss to the agent is not difficult. In other words, this is the simplest form of a civil liability lawsuit. But sometimes there are two or more commits, in these cases proving the attribution of the loss to the agents is difficult. In these cases that there are several agents, recognition of main cause and quality division of responsibilities is very difficult so that different views on jurisprudence and law presented.Key words: Responsibility ,cause& agent, Causal relationship, Division of responsibilities