This paper applies a new explanation of magic and religion to ritual taboos among fishermen. Instead of seeing the raboos as a means of relieving anxiety, the paper proposes that taboos promote cooperation by communicating a willingness to accept trad-tional patterns ofauthority. Thisapproach predicts that taboos will be more frequent in situ-ations where intensive cooperation between individuals is crucial. This prediction is tested against data on fishing societies that have been used previously to demonstrate a correlation hetween danaer and taboos. The cooperation hypothesis appears to be at least equal to the Anxiety-reduction hypothesis. In accounting for variations in taboo usage in different types of fishing. It also has the advantage of not requiring the problematical assumption that the fishermen believe that the taboos they observe actually work.