Thrombophilia can be defined as an increased tendency to thrombosis. There are several defined risk factors for thrombosis, and these are generally separated into acquired and congenital factors. Congenital risk factors include deficiencies or defects in natural anticoagulants, such as antithrombin, protein C and protein S, and genetic polymorphisms such as prothrombin G20210A and the cleavage-resistant factor mutation, factor V Leiden, which leads to a condition known as activated protein C resistance. Acquired risk factors include antiphospholipid antibodies, detected as lupus anticoagulants, and/or anticardiolipin or anti-beta2-glycoprotein I antibodies. Elevated homocysteine, immobility, increasing age, surgery, cancer, poor nutrition, pregnancy, high levels of clotting factors, and use of oral contraceptives and hormone replacement therapy comprise other risk factors. Each of these constitutes an element of increased risk, which is compounded when concomitant. There is ongoing debate regarding relative and compound risks, the value of laboratory screening, whom to screen for with these markers, and the form and duration of clinical management. This report briefly explores, from a scientist's perspective, some important issues that are sometimes overlooked.