When the British first learned of polo in Persia, the ponies used for play were measured at twelve hands two inches. The first height limit for polo ponies in England was fourteen hands in 1876. In 1896 the limit was raised to fourteen hands two inches. The limit was abolished in 1919. Currently most polo ponies are horses of normal height, averaging fifteen hands one inch.
Most ponies are of thoroughbred stock.
The breeding of polo ponies has been documented in England since 1893. The small thoroughbred stallion Rosewater holds the title of foundation sire for modern English ponies. In the United States, thoroughbreds are often bred to quarter horses to improve agility. Small thoroughbreds from Australia and New Zealand make quality ponies as well. The majority of the very best polo ponies since the 1930's have come from Argentina, where thoroughbreds are crossed with the local Criollo horses.