The demand for anticoagulation management is increasing because of a widening of the indications of treatment. A primary care clinic using near-patient testing and computer decision support software is one model of care to meet this increased demand. The study aimed to determine the cost and cost-effectiveness of primary care-based anticoagulation management in comparison with 'traditional' hospital care-based provision by means of a cost-effectiveness analysis using data from a Birmingham-based multicentre randomized controlled trial. The costs per patient per year in primary care were pound170 [95% confidence interval (CI) pound149-190] vs. pound69 (95% CI pound57-81). Sensitivity analysis demonstrated that the cost in primary care could be reduced to under pound100 per patient per year under plausible changes in the variables. Primary care provides similar levels of control to secondary care for patients on anticoagulation therapy. There is an increased cost of managing patients in primary care and at no point did primary care become a lower cost option than secondary care. Local decision-makers need to assess the increased cost of primary care anticoagulation management in terms of the potential reductions in high-cost serious adverse events.