Second-line intraperitoneal (i.p.) therapy has been demonstrated to result in surgically defined complete responses (S-CR) in 25%-40% of patients with small-volume residual ovarian cancer (microscopic disease or largest tumor mass less than 1 cm in diameter). To evaluate the influence of the surgical finding of diffuse peritoneal carcinomatosis on the S-CR rate to salvage i.p. therapy in this patient population, we retrospectively reviewed the operative reports of 70 patients with small-volume residual ovarian cancer treated on one of three phase-2 second-line i.p. trials at the Memorial Sloan-Kettering Cancer Center. Of the 11 patients with diffuse carcinomatosis, none achieved a S-CR compared to a S-CR rate of 37% (22/59) in patients without this surgical finding (chi 2 = 6.0; P less than 0.025). However, of the 7 patients with diffuse carcinomatosis treated on a cisplatin-based i.p. program, the only 2 who had previously responded to systemic platinum also experienced a response (partial) to the i.p. cisplatin regimen. In conclusion, while the surgical finding of diffuse peritoneal carcinomatosis indicates a poor prognosis in patients with small-volume residual ovarian cancer for response to i.p. chemotherapy, patients in this clinical setting with prior evidence of platinum sensitivity may experience some benefit from an i.p. cisplatin-based treatment strategy.