Preoperative serum soluble interleukin-2 receptor (sIL-2R) and CA 125 levels were measured in 183 patients with ovarian masses undergoing laparotomy. Serum sIL-2R levels were higher in the 54 patients with epithelial ovarian cancer than in the 129 patients with benign ovarian diseases (p < 0.0001). Elevated serum levels of sIL-2R (> or = 71 U/ml) and CA 125 (> or = 83 U/ml) were found in 79.6 and 77.8% of patients with epithelial ovarian cancer, respectively. Serum sIL-2R and CA 125 positivity rates correlated with the FIGO stage (p = 0.0033 and p = 0.0001, respectively). Raised serum levels of sIL-2R and CA 125 were detected in 11.6 and 7.0% of patients with benign ovarian diseases, respectively. The combination sIL-2R or CA 125 had a sensitivity of 88.9%, and the association sIL-2R and CA 125 had a specificity of 98.4% for epithelial ovarian cancer. As for the 16 patients with this malignancy who were serially monitored during and after chemotherapy, changes in sIL-2R and CA 125 levels correlated with the clinical course of disease in 62.3 and 94.3% of 53 instances, respectively. In conclusion, the serum sIL-2R assay could represent a useful adjunctive tool for the differential diagnosis of ovarian masses, while it seems to be of limited benefit for monitoring the response to chemotherapy and follow-up of patients with epithelial ovarian cancer.