 The problem of dealing with risks in deontological theories is similar to the corresponding problem in rights-based theories. The duty not to harm other people can be extended to a duty not to perform actions that increase their risk of being harmed. However, society as we know it is not possible without exceptions to this rule. The determination of criteria for such exceptions is problematic in the same way as for rights-based theories. All reasonable systems of moral obligations will contain a general prohibition against actions that kill another person. Such a prohibition can (and should) be extended to actions that involve a large risk that a person is killed. However, it cannot be extended to all actions that lead to a minuscule increase in the risk that a person is killed, since that would exclude many actions and behaviours that few of us would be willing to give up. A limit must be drawn between reasonable and unreasonable impositions of risk. It seems as if such delimitations will have to appeal to concepts, such as probabilities and/or the size of the benefits obtained by taking a risk, that are not part of the internal resources of deontological theories.