CA-125 is a sensitive, but not a specific, tumour marker especially used in the diagnosis and follow-up of ovarian cancer. Because of the elevated levels of CA-125 encountered during the etiological investigation of nephrotic syndrome (NS) a clinical study was designed to investigate the probable relationship between elevated CA-125 levels in patients with NS, with and without ascites. Twenty-four patients with NS due to non-tumoural pathologies, aged 24 to 56 (15 females and 9 males), were investigated We detected elevated levels of serum CA-125 (275.92 +/- 154.71 U/mL) in 14 (70%) NS patients with ascites (p<0.05). In the other 10 NS patients without ascites (Group 2) and in the control group, consisting of 52 age and sex-marched healthy volunteers, the serum CA-125 levels were found to be 13.60 +/- 5.12 U/mL and 8.50 +/- 5.02 U/mL, respectively (p>0.05). There was no statistically significant difference between the control group and the patients without serosal fluids (p>0.05). We concluded that serum CA-125 levels were elevated in NS patients with ultrasonographically detected ascites in the absence of an ovarian tumour or other diseases known to increase the levels of CA-125.