Asked by St. Louis congressman William Clay whether he could assure fans he had played "with honesty and integrity," McGwire said, "I'm not going to go into the past or talk about my past. I'm here to make a positive influence on this."

He also refused to address allegations of steroid use leveled against him and other ballplayers by his one-time Oakland A's teammate Jose Canseco and said he would not be "naming names."

"My lawyers have advised me that I cannot answer these questions without jeopardizing my friends, my family and myself," McGwire said.

McGwire retired in 2001. He has previously admitted using androstenedione, a precursor to anabolic steroids and a legal substance at the time.

When Clay asked what other substances he may have used, he said, "I'm not here to talk about the past."

McGwire acknowledged that "there has been a problem with steroid use in baseball" and said he is willing to help lawmakers combat the use of performance-enhancing drugs by younger players.

But he did not directly address Canseco's allegation in his remarks.