Our laboratory has discovered that blood sera of healthy men and women contain low levels of anti-HMdU (Shydroxymethyl-2′-deoxyuridine, an oxidized thymidine) autoantibodies (aAbs) (1 ,2 ) However, patients with chronic inflammatory diseases exhibit elevated anti-HMdU aAb titers. Interestingly, people at high risk for cancer, those with cancer and, most importantly, those who were diagnosed with breast, colon, and rectal cancer 0.5–6 yr after donation of the blood samples we analyzed (but not those diagnosed with nonmelanoma skin cancer) had significantly elevated anti-HMdU aAb titers (4 ). The high aAbs in apparently healthy women at the time of blood donation persisted for several years before diagnosis (3 ). We recently also showed that these anti-HMdU aAb titers depend on subject’s age and menopausal status (5 ) Our findings pomt to anti-HMdU aAb titers as being a biomarker of a potential to develop cancer even in the absence of family risk factors, which constitute the majority of cases