It is well known that one of the most evident effects of prolonged and intense physical training is an increase of left ventricular mass. This increase could have a great influence on the diastolic properties of the heart, which can now be accurately evaluated by use of pulsed- and continuous-wave of Doppler echocardiography. The aim of this study was to evaluate the diastolic function of a group of superendurance athletes (professional bicyclists, exercising more than forty hours a week). Sixteen athletes (A), aged between twenty and thirty-one years, during the period of maximal training, and 16 age-matched controls (C) were studied. All subjects were evaluated at rest with mono-dimensional, two-dimensional, and Doppler echocardiography. Diastolic (DD) and systolic (SD) diameter, posterior wall (PW), and interventricular septum (IVS) thickness were also measured. The left ventricular mass (LVM) was calculated. Diastolic function was evaluated by calculating isovolumetric relaxation time (IVR) with continuous-wave Doppler, and deceleration time (DT), rapid filling flow peak (Ep), and atrial filling peak (Ap) were evaluated with pulsed Doppler echocardiography. The LVM (A: 354 +/- 47 g vs C: 170.6 +/- 33.4, p < 0.05), DD (A: 57.7 +/- 3.9 mm vs C: 50.5 +/- 2.7, p < 0.01), PW thickness (A: 11.9 +/- 0.7 mm vs C: 8.4 +/- 0.6, p < 0.05), and IVS thickness (A: 12.3 +/- 1 mm vs C: 8.2 +/- 0.9, p < 0.05) were significantly greater in the athletes than in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)