From January 1988 to December 1992, 106 patients with advanced gynecologic cancer were preoperatively explored by clinical examination (CE) and endosonography (ESG) under anesthesia and by computed tomography (CT). Sixty-one tumors were primary and 45 recurrent; the main locations were cervical (73 cases), ovarian (10 cases), and endometrial (8 cases). All the patients were operated. This prospective study compares the data from clinical and imaging examinations with the histologic findings and the surgical reports. Accuracy of the CE, ESG, cytoscopy, and CT was respectively 79, 90, 82, and 80% for vesical involvement (ESG versus CT: P < 0.05). For vesicovaginal septum extension, accuracy of ESG (92%) was statistically better than that of CE (80%) and CT (77%). Accuracy of the CE, ESG, and CT was respectively 93, 97, and 89% for rectal involvement (ESG versus CT: P < 0.02). For rectovaginal septum extension, accuracy of ESG (96%) was statistically better than that of CE (85%) and CT (85%). Endosonography is valuable in the assessment of regional staging of advanced gynecologic cancers. Since it is realized during the clinical examination under anesthesia, this low-cost procedure is easily performed and provided no discomfort to the patients.