Ten female field hockey players were studied to determine if prolonged dynamic conditioning results in an increased left ventricular internal dimension at end diastole (LVIDD) and if this increase correlates with maximal oxygen consumption (VO2max). At peak season, echocardiograms were obtained and VO2max determined during maximal treadmill exercise. VO2max, LVIDD index (LVIDD/body surface area (BSA)), and ventricular septal and posterior wall thickness were compared to agematched nonathletic women. Mean LVIDD index was significantly greater in athletes than in controls: 29.3 +/- 0.9 mm/m2 vs. 26.3 +/- 0.6, P less than 0.005. Echocardiographic wall measurements did not differ significantly in the two groups. Mean VO2max for the athletes was significantly greater than controls: 51.7 +/- 4.0 ml O2.kg-1.min-1 vs. 41.2 +/- 2.1, P less than 0.001. VO2max correlated significantly with LVIDD index; r = 0.92, P less than 0.001. Female athletes show an increased LVIDD in response to dynamic conditioning similar to that seen in male athletes. The proficiency of athletic performance as measured by VO2max may be related to the heart's ability to increase LVIDD since there is a high correlation between VO2max and LVIDD index.