Studying addiction is tricky--you can't dose college students with drugs to find out how they react. So Leonard Howell, of Emory University's medical school and the Yerkes National Primate Research Center has been studying the next best thing to undergraduates--rhesus monkeys. (No offense to any undergraudates who may be reading!) He puts them on a cocaine-like drug to determine what causes cocaine addiction--and how it might be prevented. He has underscored the importance of the dopamine system, but his latest research also shows an important role for the serotonergic system in addiction. Dr. Howell discusses his work, and how it might lead to a way to treat addiction to cocaine and other drugs of abuse.