One hundred thirty-four introductory psychology students participatcd in a longitudinal study of seat belt usage. The model of Fishbein and Ajzen was tested, as was the construct of habit within this context. Multiple regression analyses supported the basic Fishhein and Ajzen model predictions. Attitudes and subjective norms predicted intentions, which in turn predicted behavior. Furthermore, habit predicted behavior better than intention. The following nonspurious relationships were observed in cross-lagged panel correlation tests: influence from subjective norm to intention, influence from intention to attitude, influcnce from attitude to subjective norm, influence from behavior to habit, and, of course, influence from attitude to behavior. Discussion included further consideration of the Fishbein and Ajzen model, social adaptation theory, and implications for seat belt usage.