The chronobiologic analysis has been applied to Dynamic ECG data in order to verify whether or not a circadian rhythm for heart rate (HR) and ventricular ectopic beats (VEB's) can be detected in athletes with frequent ventricular arrhythmia (range 169-2120 VEB's/hour). The study was carried out on 10 athletes (7 males and 3 females, aged 11-23 years), taking part in various sports, asymptomatic but characterized by a frequent VEB's. Data have been analysed by means of cosinor method. A circadian rhythm for HR was documented. A circadian rhythm for VEB's was validated in all but one of the athletes. The circadian acrophases for HR occur early in the afternoon. The circadian acrophases for VEB's are prominently diurnal (7 out of 10 cases). The VEB's circadian crest is not associated with the physical activity supporting a relative independency of the rhythmic generator of VEB's.