The effects of ad libitum smoking, abstinence, and 0-, 2-, and 4-mg nicotine gum on human cooperative responding were examined. Participants were provided the opportunity to respond cooperatively or independently to episodes initiated by a computer-simulated other person. Participants could also initiate episodes that ostensibly provided the other person the opportunity to respond cooperatively or independently of the participant. Working cooperatively added points to both the participant's and other person's counters. Working independently added points only to the participant's counter. Results demonstrated that abstinence decreased cooperative responses during episodes initiated by the computer-stimulated other person. Relative to abstinence and placebo gum conditions, ad libitum smoking and administration of 2- and 4-mg nicotine gum increased these cooperative responses. No gender differences were observed. The number of cooperative episodes initiated by the participants was not affected significantly by the smoking or gum conditions. Nicotine increased reports of vigor and decreased abstinence-engendered reports of depression, anger, confusion, and tension. The difference in the effects of nicotine abstinence on the 2 classes of cooperative responding demonstrates that the social contingency mediates the behavioral effects of abstinence.