A horse race is a contest in which humans place bets on the outcome of a competition involving horses. The sport has long been subject to controversy, especially regarding the welfare of the horses involved. In recent years, however, technological advances have brought major improvements in safety and security for both horses and jockeys. A wide range of technologies are now employed, including thermal imaging cameras that can detect overheating, MRI scanners and x-rays that can spot any minor or major health issues, 3D printing that can produce casts, splints and even prosthetics for injured horses, and much more.

The race procedure begins before the horses are actually saddled, when they are paraded past a group of officials, who are called stewards, in the paddock. Then, before the race starts, the jockeys must weigh in and the horses are checked for proper weight. Saliva and urine samples may also be taken to test for illegal substances. If the stewards suspect that a horse has been injected with something, it is disqualified from the race.

In most flat horse races (not steeplechases), to qualify for the race, a horse must have a sire and dam that are purebreds of the same breed. This requirement is one way to promote fairness to the wagering public and prevent “juicing” of a horse. The Jockey Club, the breed registry for Thoroughbreds, introduced the “claiming” system in 1897 to put a check on such activities, but this was done less to promote animal welfare than to prevent unfairness to bettors and owners. In fact, California banned betting on horse races in 1909, and reintroduced it only after a ballot measure was passed that required all wagers to be placed through an approved bookmaker.

A typical horse race lasts about three minutes, and is contested over a distance of one to three miles. The course length varies depending on the type of race and the custom of the country in which it is run.

For example, the Royal Ascot Gold Cup race is run over a 21/2-mile (4-kilometer) course. During the early days of the sport, steeplechases were a common form of racing, with participants running over natural terrain in which church steeples were prominent landmarks. There is evidence of these contests in the works of Homer and Xenophon, dating back to the 5th century BCE.

Many racetracks have a condition book, which is the schedule of races that will take place over a given period of time, such as a few weeks or a month. The condition book is based on the number of entries received and may be changed if necessary to meet the needs of the track and its customers. For example, a race could be shortened or canceled if the weather is poor. Also, a race could be moved from one track to another, or it might be substituted for an event that is already on the schedule.