Abstract: The question considered in this article is how liability rules and insurance affect incentives to reduce accident risks and the allocation of such risks. This question is examined when liability is strict or based on the negligence rule; and, if first-party and liability insurance are available, when insurers have information about insured parties' behavior and when they do not have such information. The conclusions are in essence that although both of the forms of liability create incentives to take care, they differ in respect to the allocation of risk; that, of course, the presence of insurance markets mitigates this difference and alters incentives to take care; and that despite the latter effect, the sale of insurance is socially desirable.