In a statement released by his agent, the 35-year-old left-hander said he only used HGH for two days in 2002 while trying to recover from an elbow injury.
"In 2002 I was injured. I had heard that human growth hormone could promote faster healing for my elbow. 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.
"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. If what I did was an error in judgment on my part, I apologize. I accept responsibility for those two days."