Abstract: The association of antiphospholipid antibodies (APA) has been reported in several cases of patients with non-Hodgkin's lymphoma (NHL) with or without thromboembolic complications. The purpose of this study was to analyse systematically the prevalence of APA and its clinical significance in lymphoma patients. Sera of 90 consecutive unselected patients with NHL were tested for the presence of anticardiolipin (aCL) antibodies and anti-β2-glycoprotein-I (anti-β2-GPI) antibodies. The patients were followed up over a median period of 14 months to note the occurrence of thromboembolism. We found APA in 24 out of 90 NHL patients (26.6%). Elevated APA were more often detected in women and in the elderly. The presence of elevated APA was not correlated with the histology and the stage of the lymphoma. None of the 24 patients with elevated APA developed a thromboembolic event in the follow-up period. Thromboembolic events were observed in 12 patients (13.3%), all with negative APA. High APA titres and the combination of positive aCL- and anti-β2-GPI antibodies, features which are known to be more strongly correlated with thrombosis among patients with antiphospholipid syndrome and systemic lupus erythematous (SLE), were very uncommon in our cohort of NHL patients (3.3%). Vessel compression by lymphoma but not elevated APA remains the main cause of thrombosis in NHL patients.