Schizophrenia is a heterogeneous disorder presenting as episodes of psychosis against the background of cognitive, social, and functional impairments. Schizophrenia has been studied extensively, and a large number of biological abnormalities associated with the disorder have been described. Many of these abnormalities have been proposed as biomarkers, some of which may represent useful endophenotypes for dissecting the etiology or pathophysiology of schizophrenia. The main molecular, electrophysiological, imaging, and psychological features of schizophrenia are described, with a critical evaluation of their utility as diagnostic and endophenotypic biomarkers. While none of these biomarkers are useful at present for clinical diagnosis, they may identify subgroups of schizophrenia or represent dimensions of the illness that can be subject to further study. With the recent identification of several promising candidate susceptibility genes, models of pathophysiology can now be generated to integrate this diverse collection of abnormalities from the molecular level of description with that of abnormal psychology.