Cardiolipin is a phospholipid of outermost layer of cells (cell membranes), mitochondrial membranes and platelets. Cardiolipins play a key role in the process of blood clotting. Anti-cardiolipin antibodies are acquired auto-antibodies produced against cardiolipins and are found in the immunoglobulin classes- IgG, IgM and/or IgA. The presence of anti-cardiolipin antibodies in systemic lupus erythematosus can be related to the development of thrombosis. Anti-cardiolipin antibodies have been found in some cerebrovascular insufficiency, cerebral ischemia and in myocardial infarction. Moreover, this anticardiolipin test also assists in the diagnosis of antiphospholipid syndrome. This diagnosis has significant implications for treatment and prediction of recurrent thrombosis and recurrent miscarriage.