This paper uses an integrated model of behavior change to predict intentions to use marijuana occasionally and regularly in a US-based national sample of male and female 12 to 18 year olds (n = 600). The model combines key constructs from the theory of reasoned action and social cognitive theory. The survey was conducted on laptop computers, and half of the sample was female. The analysis serves as a basis for discussion about using theory in various stages of planning a campaign to decrease marijuana use among adolescents. The theory, model fit, and tests of the mediation and sufficiency assumptions can be used to demarcate planners' choices about behavioral goals and intervention messages.