The relationship between infections and antiphospholipid antibodies or antiphospholipid syndrome is an intriguing question. A two and a half year old child with trisomy 21, who suffered three severe episodes of thrombosis each taking place after an infection, is described here. As high titres of IgG anticardiolipin (ACL) antibodies was registered during the second and third episodes, the antiphospholipid syndrome was suspected. IgM as well as IgG and IgA ACL antibodies have been described at different titres in a wide variety of infections, although they are not usually associated with thrombosis. In this particular case the timing of events and their association with high IgG ACL antibody titres seemed to implicate infection in the pathogenesis of the antiphospholipid syndrome. It can be hypothesized that some infections not only "trigger" antiphospholipid antibody production, but--in genetically predisposed subjects--can induce the clinical manifestations of the antiphospholipid syndrome.