The event is the second leg of horse racing's annual Triple Crown.
Barbaro was installed as even-money favorite for the 131st running of the race, which will have nine horses in the field. Barbaro was a decisive 6 1/2 lengths winner at Churchill Downs, the largest margin of victory at the Derby in 60 years, and has total earnings of more than $2.3 million.
"It'll probably be a cleaner-run race, but nothing changes for me," said Barbaro trainer Michael Matz on the Preakness Web site. "We still have to beat the same horses we beat last time."
Among other horses in the field will be Kentucky Derby morning line favorite, Brother Derek (Post Five), which won the Santa Anita Derby; and Illinois Derby winner Sweetnorthernsaint, who is the 4-1 third choice. Bernardini (Post 8) is an 8-1 choice.