The efficacy and safety of propafenone (PPF) were prospectively evaluated in 20 patients (13 men and 7 women, age 39 +/- 14 years) with atrial arrhythmias (AA) (atrial fibrillation: n = 13; atrial flutter: n = 7). All patients had arrhythmias from 109 +/- 63 minutes, (iT) without clinical evidence of heart failure. Intravenous PPF was given as a 1 mg/kg bolus over 5 minutes, with a therapeutical possibility of a second bolus (1 mg/kg) after 10 minutes if sinus rhythm was not restored. The conversion time (cT) was 6.4 +/- 2.2 minutes (range 3 to 18 minutes). In 19 patients (95%) sinus rhythm was restored and no serious adverse and proarrhythmic effects were noted in each patient. We conclude that 1) PPF is effective and acted significantly faster in controlling AA; 2) PPF appears to be well tolerated and relative safe with a low incidence of adverse and proarrhythmic effects in patients in a first aid station.