To assess the natural history of ventricular extrasystoles (VE), a 5-year follow-up of 52 professional endurance athletes was made. All remained well during this period. Forty-four accepted to undergo repeat extensive noninvasive cardiologic examination. In the 23 athletes still in activity at the second study the prevalence of total and complex VE at 24-hour Holter monitoring was substantially unchanged, while in the 21 subjects who had stopped training, complex VE were no longer present (p = 0.01 vs. baseline). Echocardiographic dimensional parameters were significantly higher in the still active atheletes than in the no longer active subjects; however, in the latter, left ventricular mass index was still greater than in a group of 40 sedentary subjects previously studied (107 vs. 81 g/m2; p = 0.001). High-intensity physical training does not seem to be harmful in athletes with complex VE, without evidence of underlying cardiac disease.