Measurement of the serum CA 125 level as a tumor marker in patients with epithelial ovarian cancer has been widely used to monitor disease status and predict survival of patient. While a number of benign gynecologic as well as benign or malignant non-gynecologic conditions are associated with elevations of serum CA 125 levels, the established normal range describes a healthy population of women. Because the metabolism and clearance of CA 125 is not well understood and mild or moderate degrees of renal impairment frequently occurs in ovarian cancer patients during treatment or course of disease, it is valuable to investigate the effect of impaired renal function on serum level of CA 125. Eighty-nine women on hemodialysis who had no other definite cause to elevate serum CA 125 level were selected at random. The age of the patients ranged from 19 to 83 and renal disease was secondary in most cases to diabetes mellitus, hypertension or glomeru-lonephritis. The creatinine clearance was less than 10cc/min for all patients. (continue)