Clinical studies on endorphines and schizophrenia are overviewed and evaluated. In the past eight years studies on endorphines have been a topic in the scientific literature. Several theories have been developed about the relation between endorphines and the severe psychiatric disease schizophrenia. On the one hand scientists believe that schizophrenia is caused by 'too less' of an endorphin in the brain. On the other hand researchers hypothesize 'too much' of this substance as the starting agent of schizophrenia. Lately Dutch researchers have developed a new hypothesis, saying that the equilibrium between different endorphines and their metabolites is disturbed in schizophrenics. By determining the amounts of endorphines in the cerebro-spinal fluid and the blood, by haemodialysis, injection of an endorphin-blocker (naloxon), 6-endorphin, FK-33-824 and des-tyrosine-y-endorphin the different hypotheses has been tested. Neither of these clinical experiments have, in the long run, produced positive results. Finally a comment is given upon this scientific development.