Objectives: To analyse the use of one or another leg as the dominant leading leg in elite 400-metre hurdle athletes. Method: This is a transversal descriptive study. All the 400-meter hurdle races of the 72 participants (34 men and 38 women) at the XIII IAAF World Championships in Athletics Daegu 2011 were studied by means of video recordings taken from the main stand of the Daegu Stadium of the eighteen 400-meter hurdle races that took place, which were later analysed using the Kinovea 0.8.4 computer application. Results: By athlete, in all male races, the dominant leading leg was the left one in 63.6% (42 athletes) and the right one in 34.8% (23 athletes) of the cases. There was only a balance between left and right in one case. In the final, 75% (six athletes) of the athletes had a left leading leg. With regard to women, the dominant leading leg was the left one in 48.6% of cases followed by the right leg in 41.4%. 10% showed a balance between the two. In the final, on the other hand, the dominant leading leg was the right leg in 87.5% (seven athletes) of cases as opposed to 12.5% with the left (1 single athlete). Significant differences (p=0.018) were found in the average final time of the male athletes depending on their leading leg. Conclusions: Most athletes attack hurdles with their right and their left leg at some time during the race, meaning they need to dominate the bilateral technique. The most frequently used leading leg is the left one, although less so in the case of women. For the first time in a top-level competition, seven out of the eight women finalists had their right leg as their dominant leg.