OBJECTIVE: A study of the utilization of drugs, particularly antithrombotic agents and anti-arrhythmic agents, in patients with atrial fibrillation (AF) with changes over time in primary health care. METHODS: Surveys were done of patients with AF over 1-year periods, 1992-1993 (n = 135) and 1997 1998 (n = 144), respectively, at a community health centre in Stockholm County. Information on the prescription of drugs was obtained from the computerized medical records. RESULTS: The rate of antithrombotic treatment increased from 62.2% to 79.2% (P = 0.001), owing to an increased use of antiplatelet agents from 36.3% to 47.9% (P = 0.037), while the use of anticoagulant agents was on an equal level (25.9% vs 31.3%). The use of any antithrombotic agent in the primary prevention of thromboembolic events in AF increased from 20.0% to 41.0% (P = 0.000). The mean doses of aspirin, when used, increased from 123 to 142 mg (P = 0.036, one-tailed student's t-test). The use of sotalol also increased, from 14.2% to 25.2% (P = 0.024). CONCLUSIONS: Despite the increased use of antithrombotic agents, there is still an under-prescription of anticoagulant agents and of doses of aspirin.