Sixty-four women with ovarian cancer and 46 controls with benign gynecologic conditions underwent cytologic and CA 125 evaluations of peritoneal fluid or peritoneal washings at laparotomy. These parameters were correlated with preoperative disease status, intraoperative findings, and preoperative plasma CA 125 levels to determine their value in assessing occult disease. No false-positive cytology reports were observed. Cytology specimens were positive in 20 of 23 patients (87%) with clinical evidence of disease who had peritoneal fluid present, but in only 18 of 29 (62%) of similar patients with no peritoneal fluid present (P less than .05). CA 125 values were elevated in 16 of 23 (69.5%) and 15 of 29 (52%) of these samples, respectively (P greater than .05). Levels of CA 125 in peritoneal fluid washings correlated poorly with the presence of obvious intraperitoneal cancer and had questionable reliability when used to evaluate patients clinically free of disease. Positive peritoneal cytology reflected the presence of ovarian cancer, but its absence did not mean that an objective response to chemotherapy treatment had occurred. Disease status correlated best with physical examination and circulating levels of CA 125.