Abstract: The study population comprised 725 Thoroughbred racehorses with fractures over a 5 year period from 2007 through 2011 at the Korea Racing Authority’s Seoul racecourse. There were 371 racing-related fractures in horses, accounting for the highest proportion of 51.2% of the fractures, followed by training-related (33.4%) and management-related (14.1%) fractures and fractures defined by pre-qualification inspection factors (1.4%). Fatal injury by racing-related fractures had the highest proportion at 32.8% of all the fractures in the study horses. The proportion of leg fractures was as high as 96.6%; this can be explained by considering the skeletal function of horses and the burden of supporting the body weight. In terms of occurrence by age, among factors for racing-induced fractures in horses, fracture occurrence rate in horses of 3-5 years of age exceeded the average rate of 0.60%. In the analysis of fracture occurrence by sex, geldings were the most frequently affected followed by male and then female horses. In the analysis of factors affecting racing-related fractures, fracture occurrence was considerably high in racehorses in which the burdened weight exceeded the average value. For burdened weight over 54 kg, there was a fracture in 219 of the 371 horses with racing-related fractures and this proportion was relatively high at 59%. When the track surface was muddy or sloppy, the fracture occurrence rate was higher than that during fast, good or humid conditions.