Since more and increasingly different species of animals are kept as companions one has to face the fact that apart from the well documented positive effects of human-animal interaction there are negative consequences as well. CALLISTO will focus on the risks of zoonotic infectious diseases associated with companion animals. To do so, we will form a multidisciplinary, multisectorial and interprofessional network of experts representing the major relevant stakeholders. In a 3 year program we will provide an overview of the current situation with regard to the role of companion animals as a source of infectious diseases for people and food animals. We will identify knowledge and technology gaps for the most important zoonoses and will propose targeted actions to reduce the risk of zoonotic diseases transferred via companion animals. Furthermore, we will keep our stakeholders and the general public informed of our results in order to contribute to the uptake of the proposed actions and to promote risk-awareness in healthy human-animal relationships. To this purpose, CALLISTO will install a total of seven Expert Advisory Groups (EAG), consisting of experts in complementary fields of interest that will meet at regular intervals in order to exchange perspectives, knowledge and ideas and to produce expert documentation that serves as input from the specific EAG to the CALLISTO Conferences. The following EAGs will be installed: EAG User Community, EAG Policy Actions; EAG Zoonotic Viral Infections; EAG Zoonotic Bacterial Infections, EAG Zoonotic Parasitic Infections, EAG Epidemiology and underlying factors, and EAG Sociology and Welfare. The CALLISTO Synthesis Conferences are the center stage of the project, where experts from all EAGs come together to engage in discussions with each other and with other representatives from outside the network. Results from the Conferences will be widely disseminated.