The aim of our study is to evaluate the diagnostic and therapeutic attitude toward endometriosis of the bladder. We have analysed four observations treated in the gynecologic service of Hotel-Dieu in Paris between January 1989 and January 1998, which represents 1.3% of all endometriosis operated during this period. Every patient underwent echography, RMN, UIV and cystoscopy. In all for cases a surgical treatment by laparotomy was realised. The choice of this way is explained by the multiple localisations of endometriosis in three cases and the impossibility of a coelioscopic treatment in the forth. The anatomopathologic exam found endometriosis in all of the cases.