Mannose-binding lectin (MBL) modulates inflammation and usually enhances clearance of apoptotic cells. We observed that the concentration and total amount of peritoneal fluid MBL does not differ in patients with and without endometriosis. Mannose-binding lectin (MBL) modulates inflammation and usually enhances clearance of apoptotic cells. We observed that the concentration and total amount of peritoneal fluid MBL does not differ in patients with and without endometriosis.