We find that the average stock-market reaction to announcements of poi
son pills is positive when the board has a majority of outside directo
rs and negative when it does not. The probability that a subsequent co
ntrol contest is associated with an auction is also positively related
to the fraction of outsiders on the board. These results are largely
driven by directors who are retired executives from other companies. T
he evidence suggests that outside directors serve the interests of sha
reholders.