Karasuyama Hospital is an acute care psychiatric hospital of Showa University, which has two so-called super emergency wards, which charges a special admission fee for accepting psychiatric emergency patients. Often with difficulties obtaining detailed information of patient background and clinical history, the initial diagnosis of acute transient psychotic disorder remains unchanged until discharge in many cases. Although the diagnosis of acute transient psychotic disorder is commonly given and clinically useful to some extent in psychiatric emergency practice, its clinical features remain undefined and hence not often subjected to academic studies. We have created a database of patients admitted to super emergency wards of our hospital between January 1, 2010 and December 31, 2014 by reviewing medical charts. Consistent with previous findings, the most common group of patients admitted to super emergency wards was those with schizophrenia. At the point of discharge, according to ICD-10, 28 patients were diagnosed with acute transient psychotic disorders. This is in comparison with 996 patients diagnosed with schizophrenia, who tended to show drastic symptoms, yet those symptoms cleared in a relatively short period of time with a low dose of major tranquilizers. Moreover, almost half of the cases diagnosed with acute transient psychotic disorders also met the diagnostic criteria of atypical psychosis. We suggest that the disease concept of atypical psychosis is important in psychiatric emergency patients diagnosed with acute transient psychotic disorder at our hospital.