The discovery of black swans in Western Australia was a shock for scientists. Today those unexpected birds have become a symbol for the disruption of the bell curve that is used for most forms of variation. Bhopal, Exxon Valdez and Société Générale have shown that, in business, the highly improbable can occur, with devastating consequences. In this article the authors take a closer look at some of these incidents, examine the effect on companies and show what you can do to prevent a Black Swan event happening to you.