The preoperative macrophage colony-stimulating factor (M-CSF) levels were measured in serum samples from 56 patients with epithelial ovarian cancer and 68 patients with benign ovarian disease who had undergone laparotomy. M-CSF values were significantly higher in the former (median, range: 2.18, 0.70-10.00 ng/ml versus 1.19, 0.17-5.54 ng/ml, P < 0.0001), and were not significantly related to stage, histology, grade of differentiation, age, and residual disease after first surgery. M-CSF concentrations were also measured in 163 serum samples drawn from patients with stage III-IV epithelial ovarian cancer at different times since the first surgery. M-CSF values were higher in the 81 samples from patients with clinically evident disease than in the 82 samples from patients with no clinical evidence of disease (median, range: 2.13, 0.60-10.00 ng/ml versus 1.05, 0.40-10.00 ng/ml, P < 0.0001). M-CSF levels before second-look laparotomy were similar in the 18 patients who showed persistent disease at surgical reevaluation and in the 11 patients who achieved pathological complete response (median, range: 1.26, 0.70-3.27 ng/ml versus 0.94, 0.46-4.23 ng/ml, P = NS). M-CSF concentrations were raised (> or = 1.70 ng/ml) only in 1 (14.3%) of the 7 samples from patients with clinically evident disease and serum CA125 < 35 U/ml, and only in 5 (38.5%) of the 13 samples from patients with positive second-look findings and serum CA125 < 35 U/ml. In conclusion, serum M-CSF levels correlated with the clinical status of disease in patients with epithelial ovarian cancer. However, the concomitant determination of serum M-CSF seems to add little to the CA125 assay alone in the monitoring of patients with this malignancy.