Concept and nosologic status of acute and transient psychotic disorders, as they appear in the tenth edition of the International Classification of Disease, have seen review from the standpoint of validation and delineation from schizophrenia and affective disorders. Current research, particularly on the epidemiology, course, and outcome, and family genetic studies indicate that these disorders are common among women in developing countries, as well as among lower socioeconomic status and rural subjects. These patients have greater frequency of exposure to stress before childbirth, a family history of acute and transient psychotic disorder (and not of schizophrenia), and a course and outcome that is different from that of schizophrenia. The findings so far support the argument that acute and transient psychotic disorders are different from schizophrenia.