Survey of the first admitted patients for nonorganic and nonaffective acute psychotic decompensation in an Inpatient Treatment Unit, as a part of a Mental HealthCenter, in a General Hospital. Preliminarily the Authors review the concept of "acute psychosis" from Bleuler to Leonhard, Wyrsch, Lanfeldt, the bouffées delirantes of the French literature, the schizophreniform disorder of the DSM III R. The acute psychosis is "a carrefour state" where many types of acute events come together: schizophrenic, affective, reactive. Sometimes, but rarely, acute psychosis is a nosographic unit. This unit needs further evidence.