The traditional NIH research project grant consists of a single Program Director/Principal Investigator (PD/PI) coordinating all efforts on an independent research project. Although this model clearly continues to work well and encourages creativity and productivity, it does not always work well for multidisciplinary efforts and collaboration. Increasingly, health-related research involves teams that vary in terms of size, hierarchy, location of participants, goals, disciplines, and structure. The multiple-PD/PI model supplements, and not replace, the traditional single PD/PI model, and allows applicants and their institution to identify more than one PD/PI on a single grant application. The goal is to encourage collaboration among equals when that is the most appropriate way to address a scientific problem. The availability of the Multiple PD/PI option encourages interdisciplinary and other team approaches to biomedical research.