The emotional climate within the home is a powerful predictor of relapse and remission in schizophrenic disorders. Research has focused on "expressed emotion" (EE), a measure of relatives' expressed attitudes about the patient. Recently, EE has become a focus of controversy. Correcting a misperception that EE research blames families of schizophrenic patients, we clarify the concepts and data base that underlie EE research, provide an operational definition of EE, and briefly review the history of EE research in schizophrenia and other disorders. Then, methodological and conceptual issues in the interpretation of these data are discussed, and implications for clinical practice and mental health policy are considered.