Through agent Randy Hendricks, Pettitte confirmed the anecdote contained in the Mitchell Report, which stated that the left-hander experimented with HGH on two occasions while rehabilitating elbow tendinitis from April 21 to June 14, 2002, when he was on the disabled list and working out in Tampa, Fla.
"I had heard that human growth hormone could promote faster healing for my elbow," Pettitte said. "I felt an obligation to get back to my team as soon as possible. For this reason, and only this reason, for two days I tried human growth hormone."
According to the report, Pettitte called Brian McNamee -- by then, a former Yankees assistant trainer who still worked closely with Pettitte and Roger Clemens -- and asked McNamee to travel to Tampa.
McNamee told the Mitchell investigators that he injected Pettitte with HGH two to four times, obtained from former Mets clubhouse attendant Kirk Radomski. Pettitte paid for McNamee's trip and expenses, but McNamee said there was no separate payment for the HGH.
Pettitte returned from the disabled list on June 14 of that season and made 19 starts through the remainder of the regular season, going 12-4 with a 3.29 ERA.
"Though it was not against baseball rules, I was not comfortable with what I was doing, so I stopped," Pettitte said. "This is it -- two days out of my life; two days out of my entire career, when I was injured and on the disabled list."
Major League Baseball did not ban HGH until the 2005 season. Pettitte said that repeated references in the media to his using steroids have not only been incorrect, but that they were "hurtful to me and my family."
"Everything else written or said about me knowingly using illegal drugs is nonsense, wrong and hurtful," Pettitte said. "I have the utmost respect for baseball and have always tried to live my life in a way that would be honorable. I wasn't looking for an edge; I was looking to heal.
"If I have let down people that care about me, I am sorry, but I hope that you will listen to me carefully and understand that two days of perhaps bad judgment should not ruin a lifetime of hard work and dedication.
"I have tried to do things the right way my entire life, and, again, ask that you put those two days in the proper context. People that know me will know that what I say is true."
Pettitte, 35, finalized a one-year, $16 million contract with the Yankees last week. He was 15-9 with a 4.05 ERA for the Yankees in 2007, his first season back in New York after pitching three years for the Houston Astros.
In a statement released by the club, spokesman Howard Rubenstein said the Yankees were made aware of Pettitte's forthcoming admission late on Saturday.
"We support his coming forward," the team said.