Abstract: The effect of liability rules on accident avoidance is studied in two types of situations in which potential victims and potential injurers act sequentially: those where victims act first and injurers second; and those where the reverse is true. What is of special interest about the working of liability rules in such sequential situations is that the party who acts second behaves in response to the party who acts first, and that the party who acts first takes this into account. The major result shown is that liability rules induce optimal behavior provided that they lead the party who acts second to act optimally if and only if the first party did so. In an important extension of the basic model considered, however, this result may not hold.