Our study investigated endurance performances in a performance-matched (running 42.2 km) group of females (N = 10) and males (N = 10). The distances examined were 10 km, 21.1 km, 42.2 km, and 90 km. Measurements included VO2max, running economy, lactate accumulation, and running speeds. Although our female subjects performed as well as their male counterparts at 42.2 km (194.8 +/- 12.9 m.min-1 vs 192.6 +/- 16.3 m.min-1), the performance for 90 km was significantly better (P < 0.05) in the female group (171.0 +/- 11.7 m.min-1 vs 155.2 +/- 14.7 m.min-1). The average fraction of the VO2max (F) sustained by each subject indicated that the females achieved their performances by working at a higher (P < 0.01) F (73.4 +/- 5.5% vs 66.3 +/- 3.7% for 42.2 km and 59.8 +/- 6.2% vs 50.2 +/- 3.1% for 90 km). The degree of decline in the fraction of the VO2max sustained as the distance of running increased was significantly less (P < 0.05) in the females. The better performance by the females at 90 km was not related to greater maximal aerobic capacity, running economy, training level, or fatty acid metabolism.