A microcomputer has been used for 6 years to assist in the running of the anticoagulant clinic for over 300 patients in a district general hospital. The dose adjustments and the time intervals to the next visit are decided automatically. The system has proved very satisfactory in practice, as shown by data presented. There is considerable saving of medical and secretarial time. There has been no equipment failure necessitating reversion to manual methods. The system produces letters (or labels), lists and continuous statistics, and allows the selection of various options, which makes it adaptable to the requirements of other hospitals.