Ajzen's (1988) theory of planned behavior was modified and used to examine antinuclear behavior. Subjects completed a questionnaire measuring their antinuclear attitudes, their perceptions of support for taking antinuclear action, and their perceptions of efficacy in this arena. Then, an antinuclear behavioral intentions questionnaire was presented, as well as several opportunities to engage in various antinuclear actions. Regression analyses indicated that Ajzen's model was supported to the extent that attitude emerged as a significant predictor of antinuclear intentions and behaviors. Subjective norms and efficacy were not significant predictors of either intentions or behaviors. Models incorporating behavior-specific attitude measures accounted for more variance than did models using more general attitude measures toward nuclear war/weapons.