Peritoneoscopy was done within 1 month of exploratory laparotomy in 30 consecutive patients, with ovarian carcinoma as part of their pretreatment evaluation. Six of the 7 patients who were thought to have ovarian carcinoma localized to the pelvis (stages I and II) were found to have advanced disease (stage III) at peritoneoscopy and thus required a change in therapy. Metastatic diaphragmatic involvement in ovarian carcinoma is common and was found in 77 percent of all patients studied. The routine shielding if the liver area ordinarily used with total abdominal radiotherapy would select these patients for therapeutic failure. Peritoneoscopy supplied reevaluable finding in 2 of 7 patients having normal physical, roentgenologic, and laboratory examinations, as well as in 93 percent of all patients stuided. "Second look" peritoneoscopy precluded the need the laparotomy in 5 to 13 patients achieving as apparent clinical remission.