The serum concentration of the tumour marker CA 125 was determined during an inflammatory adnexitis of a young woman of 22 years of age, the measured value being 478 kU/l. After the inflammation had subsided, a malignoma was largely excluded by laparoscopy; the CA 125 value had dropped to 70 kU/l. In a woman of 34 years of age who had an endometriosis that had been identified for the last ten years, as well as an acute suppurative fibrinous peritonitis, the CA 125 value was found to be 205 kU/l. On the fourth postoperative day the value was around 165 kU/l, on the 13th and 26th postoperative day 273 kU/l and 168 kU/l, respectively. There were no signs of an inflammation.