The 400-m hurdles (400 m-H) race is an event wherein the runner runs 400 m while clearing 10 hurdles arranged at 35-m intervals. This event requires techniques different from that of 110-m hurdle run and 400-m run without hurdles, including hurdle clearance on curved track, stride adjustment, step switching, hurdle clearance with either lead leg (both right and left leg attack). Furthermore, this requires not only strength and power for high-velocity running accompanied by hurdle clearance, but also physical fitness such as endurance, coordination, and flexibility. Additionally, 400 m-H takes about 50 seconds in males, similar to 400-m running; hence, it is difficult to maintain maximum velocity from the start to finish. Thus, it can be said that 400 m-H is a tactical event. This book gives an overview of previous research on 400 m-H, and discusses the research on the techniques, physical fitness, tactics, and prospects for future research to improve the performance in 400 m-H.