AbstractRicin is one of the most fascinating poisons due to its high toxicity: as little as 500 µg can kill an adult. It gained fame by its use in the so‐called ‘umbrella murder’ to kill the Bulgarian dissident Georgi Markov in 1978. Ricin also became known as a potential bio‐terror agent to which people could be exposed through the air, food, or water. The origin, biochemistry, toxicity, and analytical procedures for the determination of ricin are summarized. The homicide of Markov is described as well as recent cases of criminal ricin use. Copyright © 2009 John Wiley & Sons, Ltd.