Retroperitoneoscopy (RPS), a form of direct vision endoscopy derived from mediastinoscopy, allows exploration of the majority of the lumbar and pelvic retroperitoneal space. Over a period of three years since May 1985, we have performed 135 RPS for 107 indications in 106 patients. Twenty-two examinations were performed for the diagnosis of retroperitoneal masses or adenopathy and a precise histological result was obtained in 20 cases. In 2 cases, the hypothesis of malignant lymphadenopathy was formally excluded. Lymph node extension from 78 pelvic cancers (bladder : 52, prostate : 22, cervix : 3, endometrium : 1) were studied by unilateral or bilateral pelviscopy; RPS corrected the imaging in 24 cases and there were 4 false negatives. Seven patients with suspected lymph node recurrence from malignant diseases (3 lymphomas, 4 miscellaneous tumours) were examined : 3 recurrences were confirmed and 2 were excluded. There were 2 failures responsible for 2 false negatives. The diagnostic accuracy of RPS (94%) is superior to that of other diagnostic investigations for retroperitoneal masses and evaluation of retroperitoneal lymph nodes. In many cases, it eliminates the need for exploratory laparotomy.