Ricin, the toxic protein of the castor oil plant's seed, (Ricinus communis, Euphorbiaceae) recently has earned a great significance, as a potential biological weapon. Its production is comparatively easy, with a long shelf-life and in the form of an aerosol it seems to be ideal for terrorists. Under its effect various organs of the organism will be pathologically influenced particularly the liver, kidneys, lymph nodes and lungs. Moreover it causes hyperpyrexia and interacts with the electrolyte and hormone metabolism as well. Taking into consideration that after the intoxication there is a so called relatively symptomless "silent period" one must think of the possibility of intoxication. There is no causal therapy therefore one should start the supportive therapy as soon as possible.