Tailoring information to individual characteristics of a person is a promising line of development of self-help interventions. This article presents a three-phase methodology for developing computer-generated tailored interventions. The first phase of the development concerns the formulation of intervention objectives on the basis of analyses of the cognitive determinants of behavior. The second phase concerns the core of the development of a tailored intervention. For each objective, a so-called tailoring matrix is developed which specifies the individual characteristics to which the message will be adapted to. The tailoring matrices are the basis of the tailored messages and the tailoring questionnaire which will assess the individual characteristics. In the third phase, all the separately written messages must be integrated to one coherent intervention text and the lay-out is designed. This methodology may result in largely different tailored interventions depending on the theoretical framework used, the adaptation of the messages and the inclusion of feedback.