How old do you have to be?

There is no age limit on barrel racing. Many parents like to start their children at a very young age to get them comfortable with riding. There are children as young as 3 years old barrel racing, but their parents are right there walking beside them during the course. The horses speed never goes past trotting and usually parents put their children on pony's.
 Children as young as 8 years old compete by themselves and are comfortable with running their horses. The age to join a 4-H club is 8 years old, so usually kids start competing at their local fairs by this age.

There are many divisions of age groups in barrel racing, for 4-H it is 8-18 years old. After you reach 19 you are in a senior division at the fair and competing with other adults. Fairs usually have a separate show for people who are not in 4-H called a "jackpot" show.

Shows outside fairgrounds have no age limit their divisions are broken up by junior and senior. There is also a division in-between junior and senior which breaks down the size of the horse you are riding. If you have a horse that is under 14 hands and you are 15 years old you would compete in junior-pony class.