Some of our beliefs are based on what we see. But some others are based on what we have heard from someone else. These beliefs are based on testimony. The aim of this paper is to explore the equivalent of testimony for desires – a phenomenon I call ‘desire infection’. I argue that many of our desires come about by desire infection – just like many of our beliefs come about by testimony. But a crucial difference between the belief and the desire case is that while we have a pretty good defence mechanism against false beliefs that we acquire by testimony (if a belief we acquired by testimony blatantly contradicts a lot of our other beliefs, we reject it), we have no comparable defence mechanism against desire infection: there is no systematic screening of infected desires.