The present article outlines the different conception of catatonia from its initial description by Kahlbaum to current viewpoints. Originally considered to be an independent disease entity characterized by mental and motor abnormalities, catatonia was later viewed as a subtype of schizophrenia as it is the case in current classifications like ICD-10 and DSM-IV. Since catatonic symptoms were observable not only in schizophrenic psychoses, but also in affective, somatic or even psychogenic disorders, many researchers today consider catatonia as a nosologically unspecific syndrome. In the end, the traditional conceptions did not succeed in defining catatonia as a clinically homogeneous and valid diagnosis. An independent conception was elaborated by the Wernicke-Kleist-Leonhard school of psychiatry. Based on a precise differentiation of psychomotor disturbances, two essentially different forms of catatonic psychoses have been separated, systematic and periodic catatonias which differ in symptomatology, prognosis and treatment.