Data are reviewed which support the contention of the American Psychiatric Association and the U.S. Public Health Service that cigarette smokers may become addicted to nicotine. Available data indicate that 1) tobacco use shares many factors in common with previously studied forms of drug abuse--most notably, narcotic addiction, 2) the rate and pattern of cigarette smoking are partially determined by nicotine dose level, and 3) nicotine meets established criteria for a prototypic drug of abuse. These findings have implications for the understanding and treatment not only of cigarette smoking but of other forms of drug abuse and psychiatric disorders in which tobacco use is a cofactor.