Abstract Objective. – We report four cases of non-synchronous antiphospholipid syndrome (APS) and malignant lymphoma, which highlight the complex relationship that seems to exist between these illnesses. Methods. – In a retrospective study conducted in two departments (internal medicine and clinical hematology) of a university hospital, we collected all observations of patients with both APS and malignant lymphoma diagnosed throughout the past decade. Results. – An association of APS with malignant lymphoma was recorded in three female and one male patient, median age 42.5 years at the time of diagnosis of the first disease. In each case, the primary APS was diagnosed, with arterial thrombotic events in three cases and venous thrombotic events in one case. One patient had isolated IgG anticardiolipin antibody, whereas the others had a combination of IgG anticardiolipin antibody and lupus anticoagulant with or without IgG anti-β2 glycoprotein I antibody. One patient also had an acquired inhibitor to factor VIII:C and a chronic C virus hepatitis. The mean time apparently separating the two illnesses ranged from 18 months to 9 years, but in two cases the diagnosis of APS was delayed due to a progressive, atypical, neurological onset. In two instances, the APS took place at a distance from a cured malignant lymphoma (Hodgkin’s disease and nodal large cell B-cell lymphoma), whilst in the others it preceded a B-cell lymphoma (nodal and cutaneous, small cells and primary hepatic, large cells). Treatment resulted in complete haematological response in both cases, with disappearance of anticardiolipin antibody and lupus anticoagulant in the latter following a double autologous peripheral blood stem cell transplantation. In addition, late carcinomas (breast, kidney, thyroid) were seen in two patients. Conclusions. – Our data indicate that the diagnosis of a malignant lymphoma should be considered in patients with a primary APS and peripheral lymph node enlargement or unexplained constitutional symptoms. Conversely, a late onset of arterial or venous thrombotic diathesis after a malignant lymphoma may indicate not only late relapse of malignant lymphoma but also a subsequent APS.