The availability of low molecular weight heparin (LMWH), with associated ease of home delivery and enhanced efficacy and safety, has rendered the long-term outpatient use of LMWH feasible. Although warfarin is usually used for longterm secondary prevention, it is not the drug of choice for a variety of conditions such as antiphospholipid thrombosis syndrome, sticky platelet syndrome, and patients with malignancy and other medical conditions who have failed adequate warfarin doses. We assessed the long-term efficacy and safety of outpatient dalteparin in a series of patients with conditions associated with prior warfarin failure or potential to warfarin therapy (antiphospholipid syndrome). The results of this study, detailed herein, demonstrate that long-term dalteparin is highly effective and safe when used as long-term therapy for secondary prevention in selected prothrombotic disorders.