Anticardiolipin antibodies (ACA) are one of a number of autoantibodies found in patients with systemic lupus erythematosus (SLE) and their presence has been associated with clinical features of the antiphospholipid syndrome (APS). The aim of this study was to determine which clinical features are associated with a positive anticardiolipin antibody in Irish patients with SLE. Ninety-five Irish patients with SLE were studied. All were examined thoroughly, had their full history taken, and had case records reviewed. The presence of any clinical feature associated with the APS was noted. Sera from these patients were tested for IgG and IgM ACA. The only significant association found was between a history of venous thrombosis and the presence of ACA, although several other features were more common in ACA positive patients. There were no significant associations with one or other isotype. This study serves as a reminder to consider the possibility of venous thrombosis, and other clinical features, if an SLE patient is positive for ACA.