No one thing, no "negative" thing, led to his decision to retire after 26 years in Congress, even though he was urged to seek re-election, Kyl told supporters in a letter.
"Simply put, it is time -- time to do something new, time to have a more flexible schedule for my family, and time to give others an opportunity," Kyl said. "My health is fine, I'm confident I could win re-election, and, while I don't like some aspects of political life, they have been worth enduring because of the tremendous opportunity I've had to represent Arizonans."
He said he looked forward to counseling other conservative candidates who share his views.
"After my family and faith, my desire to advance conservative principles is the animating force in my life," Kyl wrote. "To those who say, 'You can't stop now, there is so much to do and we're on the cusp of taking control of the Senate,' I simply note that there will always be unfinished business in advancing the cause of freedom."
Not focusing on a re-election campaign also means "I can devote the next 22 months mostly to my job of serving you," Kyl said.
With his announcement, Kyl joined Sens. Joe Lieberman, Ind-Conn.; Kent Conrad, D-N.D.; Jim Webb, D-Va., and Kay Bailey Hutchison, R-Texas, who said they will leave the Senate at the end of their terms.
Kyl, elected to the Senate in 1994, is the Republican whip, second-in-command to Senate Minority Leader Mitch McConnell of Kentucky. He also served four terms in the U.S. House of Representatives.