Results are summarized from 17 studies in which intravenous nicotine was evaluated in self-administration paradigms. Six species, ranging from the albino rat to the human, have been tested under a variety of schedules of reinforcement, and as a function of several pharmacologic manipulations. Under certain environmental conditions, it is clear that nicotine can serve as a reinforcer. However, nicotine differs from many other drugs of abuse in that the range of environmental conditions under which it serves as a reinforcer appears to be more restricted.