The present paper delineates a three-step algorithm for the analytic network process (ANP) structure design. When defining the decision goal and the alternative set, one can use the three-step algorithm proposed in this paper, first, to specify the decision criteria, and second, to outline the structure of the ANP problem. To ease the process of ANP structure design, we present two novel data structures: the multiple-effect tree and the multiple-criteria tree. The multiple-effect tree helps explore the apparent consequences of a given event or state--known in this paper as the decision alternatives--whereas the multiple-criteria tree is considered the missing link between the multiple-effect tree and the ANP structure. Employing the approach presented in this paper will help detect any mistakes in the ANP structure design. A numerical example is provided in the final section of the paper to better articulate the ideas.