Disaster preparedness is defined as actions that ensure resources necessary to carry out an effective response are available before a disaster. Disaster preparedness requires a thorough understanding of the factors that influence performance or nonperformance of disaster preparedness behaviors (DPB). The major aim of this research was to further our understanding of DPB based on the theory of planned behavior (TPB).This was a cross-sectional study of factors determining of DPB in a representative sample of 1233 Tehran inhabitants. Measures derived from the TPB were obtained in the unprepared and prepared people.Consistent with the theory, intentions to do DPB could the person predicted from attitudes, subjective norms, and perceived behavioral control with respect to DPB; and actually doing DPB was strongly related to intentions and perceptions of control assessed in the prepared people. Theoretical and practical implications of these findings are discussed.An effective intervention will not only have to encourage people of the desirability of DPB, but also to provide them with the skills and means to do it. The more strongly they can be made to feel that they have control over DPB, the more likely they are to carry out their intentions. That is, heightened perceived control tends to strengthen people's motivation to do DPB.theory of planned behavior; disaster; preparedness.