Eventing is an equestrian event comprising dressage, cross country and show jumping, also called stadium jumping. This event has its roots in a comprehensive cavalry test requiring mastery of several types of riding. It has three main formats: the horse trials or one-day event (ODE), two-day event and the three-day event (3DE), which in reality now runs four days at some competitions. The sport was once referred toas "Militaire", and there is also a format in which riders complete all three events in one day, called a "horse trial". Also, a "combined test" is a variation of eventing which encompasses any two of the phases, most commonly dressage and show jumping, but will sometimes be cross-country and show jumping or cross-country and dressage.
A three day event begins with the dressage test, performed in an arena twenty metres by sixty metres in area. The program has twenty movements, and all three basic gaits are required, the most difficult movements being frequent changes in tempo and gait, the counter canter, and counter changes of hand at the trot.
The speed and endurance test takes place on the second day. This is the core of the three-day event and is completely ruled by the clock. Cross country requires both horse and rider to be in excellent physical shape and to be brave and trusting of each other.
The third test is one in which the combination of horse and rider is tested under various conditions over a course of obstacles. It is intended to demonstrate the horse’s freedom, energy, skill, speed and obedience in jumping as well as the rider’s horsemanship. The competitor incurs penalties for exceeding the time allowed, for knocking down or refusing to jump an obstacle. The winner is the competitor who finishes with the least number of penalties.