Hypercoagulable states typically result in arterial and/or venous thromboembolism. Routine coagulation tests do not identify affected patients and thrombophilia testing detects, at best, 50% of patients at risk. We hypothesise that the OHP can differentiate patients with various hypercoagulable states from a control group. The OHP is a global haemostasis assay of fibrin generation and lysis in citrated plasma. It produces a number of parameters for comparison. We established reference ranges with plasmas from 100 normal donors, then assayed plasmas from 90 clinically hypercoagulable patients being tested for a lupus anticoagulant. A further 81 patients with demonstrable antiphospholipid antibodies (APLAs) were then assayed. Statistical analysis involved calculation of means, medians, standard deviations and Mann-Whitney testing. All parameters tested were significantly different in the clinically hypercoagulable group (p<0.001), demonstrating accelerated fibrin generation and markedly reduced fibrinolysis. On subgroup analysis patients with arterial (8) or venous thromboembolism (30), antiphospholipid antibodies (9), normal or complicated pregnancy (22) and autoimmune diseases (12) all showed significantly increased fibrin generation and lysis compared with controls. The subsequently tested 81 patients with APLAs also showed a significantly hypercoagulable OHP compared with controls (p<0.01). APLA positive patients with thromboembolism showed a non-significant trend to accelerated fibrin generation and delayed fibrinolysis when compared to those without thromboembolism. APLA positive patients taking warfarin showed significant hypercoagulability when compared with APLA negative patients on long term warfarin therapy (p < 0.01). The OHP clearly identifies patients with clinically hypercoagulable states, even in the presence of warfarin. Fibrin generation is increased and fibrinolysis delayed. We postulate that the OHP may identify patients at high risk of thromboembolism.