Prostate cancer is a polyclonal tumor. There are about 70 bis 75% responders after hormone therapy among previously untreated patients in EORTC trials. Therefore 25 to 30% of the tumors are resistant to androgen. Surgical and hormonal castration show similar results. After progression under hormone therapy response can be reached with antiandrogenic therapy in 30 to 38%. All this leads to the conclusion that it is necessary to base treatment on tumor adaptation and selection. Cell clones insensitive to androgen therefore need cytostatic chemotherapy. It is not yet proofed whether polychemotherapy really shows better results than monotherapy does. Following the thesis of a polyclonal tumor, therapy of advanced prostate cancer must be based on hormone therapy and cytostatic chemotherapy. Prostate specific antigen is a marker for an early recognition of progression.