There is only a limited amount of safe knowledge on the course of schizophrenic psychoses, although 100 years have passed since their first description as "Dementia praecox". 2 main reasons may account for this: On the one hand most studies suffer from more or less serious methodological shortcomings, which do not allow to generalize the results. On the other hand schizophrenic psychoses are possibly not one homogeneous disease with one uniform etiology and a relatively uniform course, but rather a group of diseases with hetereogenous causes and therefore hetereogenous courses as well.