The rules of polo are many and somewhat complex. They are established by the United States Polo Association (USPA) and are reviewed annually. In this section every attempt will be made to explain the rules to non-players in a simplified version yet attempting to be as accurate as possible without becoming hyper-technical. Obviously the only correct source is a current USPA rule book but this is an effort to abridge a lengthy subject.

Play commences when the umpire bowls the ball among the players who have lined up at midfield. Each team is lined up on the same side of center line of the goal it is defending. [See Rule 20]. The umpire bowls the ball hard and underhand. The players try to strike the ball and advance it toward their goal. The eight players are all scrambling for the ball and the line of the ball can change many times in a matter of seconds so fouls frequently occur at this juncture. Each team tries to hit the ball toward their goal. Should a goal be scored by a team, the teams then change goals. Teams also change goals after each chukker. These rules insure there is no advantage due to wind conditions. As the field is as flat as possible with the grass cut short and usually well tiled for drainage, play is equal for both sides.

The game is won by the team with the most goals and goals are awarded by handicap (a team with a higher aggregate handicap gives up the difference to the other team), by successful penalty shots, by the umpire if a severe infraction occurs, and, of course, by a team scoring by hitting the ball through the goal posts. While it is often said that there are no tie games in polo, players can and do call a game a tie if the weather conditions dictate. Otherwise, the game goes into sudden death overtime where the first team to score wins.

A ball sitting on the line between the goal posts is still in play. Balls must be hit between the goal posts or any line extended upward from the posts. [See rule 18]. Play is continuous unless the umpire blows the whistle. If a whistle is blown the clock stops. Should a team hit the ball over the end line the defending team will put the ball back in play by knocking it in from the end line where it has been spotted by the flag person. If the ball is hit behind the end line of the goal being defended by a defending team player a safety occurs. This results in a penalty that under Penalty Six which means a free shot at the ball for the offensive team sixty yards back from the spot where the ball crossed the end line. None of the team players who committed the safety can be within thirty yards of the ball. The opposing team may place themselves where they wish. Penalties are rated in terms of severity. The general rules are that the more dangerous the infraction or if the team fouled against was in scoring position the more severe the penalty.

Penalty One means the team fouled is awarded the goal and the ends are not changed.

Penalty Two is a free hit at the ball either from the thirty yard line nearest the fouling team's goal or if the team Captain prefers from the point the foul occurred which is usually more advantageous. No defense is allowed the fouling team.

Penalty Three is from the forty-yard line and the defending team must remain behind the end line until the ball is hit or hit at. Defenders may shoot outward between the goal posts after the ball is hit.

Penalty Four is a free hit from the sixty-yard goal line. The goal can be defended. This is probably the most common penalty shot.

Penalty Five is from midfield at 150 yards. The umpire can also allow for an alternative spot from where the infraction occurred. This is sometimes referred to as a Penalty 5(b). No defending players can be within thirty yards of the ball. Penalty shots made from midfield are extremely rare.

Players can also be ejected from the game for conduct prejudicial to the game or a deliberate dangerous foul. Substitutes may or may not be allowed and if a substitute is allowed the player must be of an equal or lesser handicap and the handicap of the team remains the same. Penalties result from infractions of the rules such as, in order of frequency:

1. Crossing the line of the ball i.e. not having the right of way. The more this endangers a horse, the more severe the penalty.
2. An illegal bump of an opposing player i.e. at an angle of forty-five degrees or greater.
3. An illegal hook. Either the player hooked too high or the other player was not in the act of swinging. No player may hook his opponents mallet unless all of the mallet being hooked is below the opponent's shoulder. This infraction is the high hook.
4. Dangerous riding is a foul. i.e. riding too fast to bump another player. There the relative speed of both horses is important. The relative course of the horses is also a factor. Zig-zagging is prohibited. Blindsiding is illegal. Players cannot bump from behind.
5. Two players against one is not allowed.

Players of little playing experience sometimes make mistakes from misplaced enthusiasm. High - goal polo is somewhat laxer on the dangerous riding issue because of the higher skill level. All of these areas are subjective to some degree but the umpires are totally in charge. No player may appeal in any manner to the umpire for a foul. This does not prevent the team captain (usually Player Three) from discussing a matter with the umpire but it considered bad form to whine, complain, and/or comment as a player.