The castration of a stallion is a significant intervention into his anatomy, physiology, temperament and behavior. Combination of physical and character traits of racehorses and interplays with the jockeys is necessary For excellent athletic performance and success on the race track. People hold a discussion how the castration of the stallion affect its athletic performance and success on the racetrack. In this thesis, we want to confirm that the castration of an excellent racing stallion will not affect its subsequent athletic performance and success on the race track. Therefore, the results will be compared with several groups of stallions and geldings in a steeplechase with the longest tradition in the Czech Republic - the Velká pardubická. It will also have a respect to the experience of trainers and riders on the differences of training with stallion or gelding. The results of this research may lead to new specific arguments in this unending debate. The introductory section summarizes the findings of the anatomy and physiology of the reproductive system of a stallions. These are essential for the understanding of the following section, which describes procedures for castration of a stallions, possible complications and its effect on the physiology, physique and character of the individual. Velká pardubická steeplechase is rightly regarded as the toughest horse race in continental Europe, whose history began in the 70s of the 19th century. The race course changed several times in the past, due to both World Wars and later with regard to the safety of horses and riders. Currently, the race course measures 6,900 meters and has 31 obstacles. The Velká pardubická was attended by 1,043 horses, some of whom participated in the race several times. Overall, there were 1,658 starting horses - 455 stallions, 397 mares and 806 geldings. All these horses were divided into 5 groups. The horses were evaluated based on the ranking from first to fifth place. All data were entered and subsequently analysed in the statistical program SAS Enterprise Guide 4.3. For each period were realized descriptive statistics of each sex and data set. Two-sample tests were used for comparing the athletic performance of stallions with geldings.