From October 1993 to February 1998, 33 cases of fetal cardiac arrhythmia were investigated by doppler-echocardiography at the Lille infantile and congenital cardiology department. Extrasystolic arrhythmias were the most frequently encountered disorder (25 fetuses, i.e., 76% of cases: 24 instances of extrasystolic auricular arrhythmia and one case of extrasystolic ventricular arrhythmia). They were invariably benign, and apart from one case only required standard monitoring. Tachycardia was observed in 15% of cases (three cases of supraventricular tachycardia [SVT] and two cases of auricular flutter [AF]). In no instance was a cardiopathic syndrome noted. A number of efficient treatments have been described, but the prognosis is often poor in the presence of hydrops fetalis. Direct fetal treatments (cordocentesis) are currently under evaluation, and at present can only be used as a last resort. In our series, one fetus died 15 minutes after transplacental Flecaine (flecainide) administration. Two of the three SVT and the two AF cases were successfully treated. Bradycardia, which was unassociated with extrasystolic arrhythmia, was found in 9% of cases. It is concluded that Flecaine is probably the treatment of choice for supraventricular and ventricular fetal tachycardia, as it has no teratogenic effect and crosses the placenta at a fetal concentration that is 80% of the maternal level. However, the administration of this drug is not without risk. It is known to possess certain negative side effects, and its pharmacological profile and maternal and fetal health risks have not yet been fully investigated. At present, no entirely safe and efficient treatment for fetal cardiac arrhythmia has been found.