Whether the harm for which compensation is sought in an action in tort is regarded as a single indivisible loss or a plurality of losses can have a number of important ramifications for the law of tort, for example, in considering compensable damage, the apportionment of responsibility between multiple tortfeasors, and the application of limitation periods and (where they exist) caps and thresholds. These issues may have particular significance in the context of mass torts, and raise questions of private international law and civil procedure as well as substantive tort law. They are also of considerable practical importance for insurers. In this comparative study, country reports from twelve legal systems and special reports on private international law and insurance provide an insight into the interaction of tort law, civil procedure, and insurance in this hitherto largely neglected area of legal science.