Antiphospholipid syndrome is defined by recurrent thrombotic events and fetal losses in the presence of anti-phospholipid antibodies detectable by beta 2 glycoprotein I-dependent anti-cardiolipin and/or lupus anticoagulant assays. Thrombosis can occur in any vascular district but deep veins and cerebral arteries represent the most frequent sites. Both early and late fetal losses have been reported in women affected by the syndrome as well as pre-eclampsia. Beta 2 glycoprotein I-dependent anti-cardiolipin and lupus anticoagulant are the formal laboratory diagnostic tools; new assays appear to improve the diagnostic power, but larger validation studies are needed before accepting them on a routine basis. In spite of the improvement in our knowledge on the pathogenic mechanisms of the syndrome, the standard therapy is still based on anti-platelet or anticoagulant drugs both for vascular and obstetrical problems.