A tetrathlon (from the numerical prefix "tetra-" meaning four) is a team competition organized by Pony Clubs for its members.
There is no minimum qualification standard to compete, but contests are only open to active pony club members (in the US this means those who have attended at least three rallies that year).
Competitors are required to shoot at stationary targets using .177 calibre air pistols from a range of 7 or 10 metres depending on their age.
Each course also includes a hazard section, containing a swinging gate which must be opened and closed while remaining on horseback, and a slip rail, through which riders lead their horse after dismounting.
Runners do not run against each other directly as in a marathon or race; instead start times are staggered at one-minute intervals.
These tend to be held during one day during the winter months when weather conditions are less favourable for the equestrian element.