The aim of this echocardiographic study was to evaluate the effects of long-term endurance training on cardiac structure and function in three different age groups of 48 healthy middle-aged and old former or still active male cross country skiers (23 in age group I: age 58.6 ± 2.2 years; 21 in age group II: age 74.9 ± 2.2 years; four in age group III: age 89.5 ± 1.9 years). The two oldest age groups were combined and compared with age group I. No significant differences in left atrial or ventricular dimensions between these two age groups were found. A high proportion of enlarged left atrial dimensions were found among all subjects with 80% exceeding the upper reference limit of 40 mm in diameter (LADs) and 94% exceeding the upper reference limit of 20 cm2 in area (LAAs). Mean values for LADs (mm) and LAAs (cm2) were: group I: 41.9 ± 4.7 and 24.7 ± 3.3; group II: 43.5 ± 4.8 and 25.2 ± 3.7; group III: 44.5 ± 4.7 and 25.8 ± 3.7. Left ventricular diastolic diameter exceeded the upper reference limits of >54 mm in 20 subjects among all. The groups had preserved systolic and age-related diastolic function.