Résumé : Acute arrhythmia is a condition covering a wide variety of rhythm disturbances. The aim of this article is to give practical recommendations for the management of the patient presenting with an acute arrhythmia. We discuss bradycardia and tachycardia. Tachycardias are divided into the small QRS complex tachycardias and the wide QRS complex tachycardias. Other important issues are the distinction between the hemodynamic stable and unstable patient and the need for trombo-embolic prevention of the patient with atrial fibrillation. Flowcharts with diagnostic means and therapeutic schemes as well as a table with practical considerations for electrical cardioversion are provided.