The authors present 2 cases of infections in which the presence of antiphospholipid antibodies (APL), anticardiolipin and anti-beta2-GP1, was associated to the occurrence of significant thrombotic events: 1) a 55-year-old male patient whose serology (indirect immunofluorescence) revealed Coxiella burnetii infection (phase 2 antigens) with IgG at 1,600 and IgM at 50 (significant titer: IgG>or=200 and IgM>or=50); 2) and a 20-year-old male patient with a CMV infection confirmed by serology (IgG: 44 U/ml, significant threshold 6, IgM: 2.1 U/ml, significant threshold 0.9).