The natural history of patients with Wolff-Parkinson-White (WPW) syndrome remains an intriguing question with respect to clinical decision-making, since serial electrophysiologic data spread over several decades in the same patient are not available in the literature. To study the age-related changes in WPW syndrome, we compared two separate groups of patients referred to this Medical Center for electrophysiologic studies because of a clinical presentation with significant arrhythmias. An elderly group of 42 patients aged 50 years or more were compared with a younger group of 51 patients aged 15 to 30 years. The groups were comparable in terms of clinical presentation, including the number of patients who had reported syncopal episodes and those requiring cardioversion of their tachyarrhythmias. Baseline electrophysiologic variables such as sinus rate; sinoatrial conduction time; corrected sinus node recovery time; AH interval; and effective refractory periods of the right atrium, atrioventricular (AV) node, and right ventricular muscle, were significantly greater in the elderly group. Similarly, the anterograde effective refractory period of the bypass tract, the shortest atrial pacing cycle length with 1:1 anterograde conduction via the bypass tract, retrograde effective refractory period of the bypass tract, the shortest ventricular pacing cycle length with 1:1 retrograde conduction via the bypass tract, the shortest consecutive preexcited R-R interval during atrial fibrillation, and the cycle length of orthodromic atrial ventricular reciprocating tachycardia were significantly greater in the elderly group.(ABSTRACT TRUNCATED AT 250 WORDS)