A report from a Study group, proposed by A. J. Camm, London, of the Working Groups on Arrhythmias and Cardiac Pacing of the European Society of Cardiology; co-sponsored by the North American Society of Pacing and Electrophysiology. The Study Group was convened on 29 August 1997 at Saltsjobaden, near Stockholm. The meeting was chaired by A. J. Camm, London, and C. M. Pratt, Houston. Based on the presentation and discussions, a first draft of the documents was prepared by C. Pratt and J. Camm which was then circulated to all members three times for their review. All members of the Study Group approved the final manuscript. This report represents the opinion of the members of this Study Group and does not necessarily reflect the official position of either society.The meeting of the Study Group was made possible by unrestricted educational grants from Medtronic, Guidant, Proctor & Gamble, Berlex and Sanofi.Also, presented, in part, at the Cardio-Renal Drugs Advisory Board meeting of the Food and Drug Administration, Bethesda, Maryland, on 30 April 1999.