Functional magnetic resonance (fMRI) has an important role in the study of the vulnerability to psychosis: it is an essential tool to search for endophenotypes that can let us to understand the pathophysiological mechanisms of schizophrenia and increase the ability to predict the onset of the illness. In this review are summarized results of the fMRI studies conducted on individuals at enhanced risk for developing psychosis, for clinical or genetic reasons. The cerebral activity in this kind of subjects appear in most cases more similar to that of individuals affected than to that of normal controls; this increases the possibility, in the future, for a diagnostic role of the cerebral activation. Nevertheless the technology is too young and the studies are too heterogeneous to reach conclusive results.