A young woman had a history of spontaneous venous thromboembolic disease which recurred on several occasions after cessation of treatment with oral anticoagulants. The presence of antiphospholipid antibodies (lupus anticoagulant and a high titre of lgG class anticardiolipin antibodies) in the absence of other clinical and serological features of systemic lupus erythematosus (SLE) confirmed a diagnosis of primary antiphospholipid syndrome (PAPS). Antinuclear antibodies (ANA) were positive (1:1280; speckled pattern). Twelve years after the first thrombotic episode she fulfilled criteria for the classification of SLE (antinuclear antibodies, platelet count < 100 x 10(9)/l, anti-dsDNA antibodies, Coombs' positive haemolytic anaemia). She suffered a myocardial infarction while adequately anticoagulated and developed polyarthritis and immune complex-mediated nephritis over the next 3 years. This case history supports suggestions made by others that a strongly positive ANA test in a patient diagnosed with PAPS may be a harbinger for the development of SLE. Such evolution can take place over more than 10 years.