68 patients with rhythmical disorders unresponsive to treatment with one or several antiarrhythmics (quinidine derivatives 52 patients, amiodarone 28 patients, beta-blockers 24 patients) were treated by mouth with propafenone, with a mean postponement of 5.6 +/- 8.5 months (1 day to 33 months). Auricular arrhythmia was observed in 41 patients with the following results: 16 successes among the 24 patients with paroxysmal fibrillation of flutter, 3 successes among the 8 patients with an arrhythmia reduced by cardioversion, and 3 successes among the 9 patients with auricular tachycardia, including 6 systolic tachycardias. Of 8 patients with an intranodal reciprocal rhythm, 7 were treated successfully with propafenone, which acts on the retrograde part of the cycle. Successes were also recorded in 2 out of 3 patients with Wolff-Parkinson-White syndrome. In 19 cases of ventricular tachycardia, propafenone proved to be efficacious in 3 out of 5 cases presenting rapid discharges and in 7 out of 14 patients with continuous arrhythmias, notably those with a catecholaminergic component. Side-effects were digestive (5 patients), cardiac decompensation (3 patients), asthenia and asthma (1 patient) and the transformation of a flutter from 2/1 to 1/1 (1 patient).