The protection of chemical plants against terrorist attacks became a new challenge after 11 September 2001. In a recent guideline the German Major Hazard Commission describes a '' security analysis '' to assess the risk of terrorist attacks on chemical plants. Whereas a complete protection never will be possible, a number of well known security and process safety measures are available to reduce the risk, thus making chemical plants to a less attractive target for terrorists. However, conflicts have to be solved between a possible need not to disclose safety information for security reasons and the public's right to know.