Characteristics of antiphospholipid syndrome (APS) clinical variants and criteria of the disease diagnosis are presented. Comparative analysis of modern laboratory methods of APS diagnosis is given, including detection of lupoid anticoagulant, determination of anticardiolipin antibodies, specific antibodies to phosphatidylserin, phosphatidylinositol and phosphatidylethanolamin, as well as to b-2-glucoprotein 1, annexin V and prothrombin. Consideration of diagnostic sensitivity and specificity of tests allows to develop   an optimal algorithm of APS diagnosis. Problems of clinical interpretation of laboratory results are discussed.