In the first part of the article the history, chemistry, origin, biological effects and laboratory detection of dioxins were reviewed. In the second part a concrete Hungarian case of 2007 and its consequences are analysed. Altogether 83 guar gum lots contaminated with dioxin and/or PCP were imported to Hungary. 324 establishments were concerned in the legal obligation to recall their products or report to the authorities, primarily the producers of ice-cream, bakery products, instant drinks, fruit products, dairy products and food supplements. Most of the establishments, 267 of them, co-operated with the authorities. 24 businesses recalled their raw materials, semi-finished or finished products. This was the first time that the Hungarian food chain safety authority was involved in a nationwide series of actions. Some lots of contaminated food additives were processed, but the dioxin or PCP content of most finished products was below the maximum limit due to dilution.