Abstract
Irving Gottesman was one of the leading psychopathologists and behavior geneticists of our time, greatly influencing our basic conceptualization of the transmission of schizophrenia and other major mental disorders in ways that impacted research programs around the world. Here we highlight his landmark twin studies of schizophrenia, his introduction of the concept of endophenotypes, and his role in providing the conceptual base for vulnerability/stress models of schizophrenia. His ability to influence our basic assumptions about the nature of genetic factors, environmental factors, and their interaction in the onset and course of major mental disorders was truly remarkable.