Quality assurance programmes for ACT should be developed and implemented in clinical departments as well as in primary care. ACT should be concentrated on fewer hands in the clinical unit. Cooperation and communication between clinical departments, the primary health sector and laboratories should be improved. More patients should be provided with written instructions. All hospital laboratories should join an external quality assurance system, INR should be used as a measuring unit for prothrombin time values so that results are comparable. Other output or dissemination activity: The impact is not evaluated, however, the published results was a.o. the direct cause for the launching of a Danish project on quality improvement in ACT, and the occasion for an initiative to introduce INR in Norway.