In this paper,we reviewed the concept of “elementary phenomena”,which was used by K. Jaspers and the French Lacanian school of thought for the differential diagnosis of psychosis. This concept can provide a useful index of schizophrenia（especially paranoid schizophrenia）. We psychiatrists can use elementary phenomena as a qualitative index of schizophrenia, not as a quantitative index（as is used by an operational diagnosis system）.
 For Jaspers, elementary phenomena have 5 features :（1）elementary phenomena arise primarily（not deducted by preceding psychical experience),（2）elementary phenomena arise as a non-sensical experience,（3）elementary phenomena invade the schizophrenic patient immediately,（4）elementary phenomena have an “overwhelming power”on the patient,and （5）elementary phenomena underlie psychotic symptoms in the later stage. Jaspers thought of elementary phenomena as a primary expression of his “process”,which is thought to be a specific cause of endogenous psychoses.
 In France,Lacan inherited Jaspers’elementary phenomena. In his doctoral dissertation（1932）,Lacan stressed that delusions arise “primarily”. He thought that delusional interpretation is not deducted by any other preceding psychical experience, and is one of the elementary phenomena. Later, in the 1950s, Lacan aimed to “define Jaspers’process by the most radical determinants of man’s relation to the signifier”, and he redefined elementary phenomena as a sudden emergence of an enigmatic signifier and non-sensical power to the patient.
 We propose that Jaspers is one of the founders of modern descriptive psychopathology, and it is important to take note of his description.