A 57-year-old woman with a history of transient ischaemic attacks and six recurrent foetal losses accompanied by elevations of antiphospholipid antibodies was diagnosed as having a "primary" antiphospholipid syndrome. She was followed up for 5 years, and she developed anaemia, leucopenia and splenomegaly. A bone marrow trephine was diagnostic of Waldenstrom's macroglobulinaemia. A false positive serological test for syphilis was demonstrated and apparently had been noted in her second pregnancy more than 20 years prior to her presentation with an antiphospholipid syndrome. There had previously been no indication to perform serum electrophoretic studies. This case illustrates the importance of this investigation in any middle-aged patient presenting with an antiphospholipid syndrome and a monoclonal gammopathy This finding might presage the development of a more serious condition, even years later (as in our patient).