It has been suggested that gender differences in running should disappear as distances increase, particularly past the marathon. This suggestion is primarily based on differences in fuel utilization, muscle damage following exercise, relative improvements in performance over the past decades, and on the analysis of marathon vs. ultramarathon performances of men and women. We reasoned that the best comparison of the potential of a human is by the use of world best times, which should be reasonable indicators of the effect of distance on relative performance of women and men. We compared current world best running performances at distances from 100 m to 200 km. Records as of December 2002 were obtained. T-tests analyzed speed differences between genders, and regression analysis tested the percent differences between men and women across distance. Speeds were different, with the average difference being 12.4% faster for men. There was a significant slope to the speed difference across distances in that longer distances were associated with greater differences. These results may be confounded by the reduced number of women in longer distance events. Furthermore, the proposed metabolic advantage for women because of increased fat metabolism may be masked by regular feeding during endurance races.