WASHINGTON – Sitting biceps-to-biceps, some of baseball’s biggest stars told Congress yesterday that steroids are a problem for the sport but denied they are widespread. Mark McGwire nearly came to tears and refused to say whether he took the performance-enhancing drugs during the historic home run summer of 1998 or any other time.

On a day of extraordinary theater, the House Government Reform Committee attacked baseball’s new steroid policy, questioning five current and former players.

Under oath, Jose Canseco – whose best-selling book “Juiced” claims steroids are rampant in baseball – repeated his admission that he used them. Sammy Sosa and Rafael Palmeiro said they didn’t. Mr. McGwire repeatedly avoided a direct response, saying his lawyers advised him not to answer certain questions.

“If a player answers ‘No,’ he simply will not be believed,” Mr. McGwire said. “If he answers ‘Yes,’ he risks public scorn and endless government investigations.”

Asked whether he favored a tougher policy, Mr. McGwire responded: “What anybody can do to improve it so that there’s no more meetings like this, I’m all for it.”

And Mr. Canseco reversed course from the book, saying he now is against using steroids.

It was an extraordinary sight – some of the top names in baseball history wearing business suits on Capitol Hill instead of uniforms on a diamond. Mr. McGwire wore a green tie, being that it was St. Patrick’s Day.

Two top sluggers who were not present testified in 2003 to a San Francisco grand jury investigating a steroid-distribution ring: Barry Bonds of the San Francisco Giants and Jason Giambi of the New York Yankees.

In a tense scene, Mr. Canseco sat at the same table as the other players as he told the lawmakers that he could not fully answer their questions because of concerns his testimony could be used against him.

During a break after the players’ opening statements, five of the stars gathered in one nearby room, and Mr. Canseco went to another.

Mr. McGwire, choking back tears, said he knew that steroid use could be dangerous and would do whatever he could to discourage young athletes from using them.

“What I will not do, however, is participate in naming names and implicating my friends and teammates,” said Mr. McGwire, who ranks sixth in major league history with 583 homers.

Mr. McGwire did say he was willing to be a spokesman against steroids: “Steroids are wrong. Don’t take them. It gives you nothing but false hope.”

The hearing came after committee members accused baseball of ignoring its steroids problem for years and then, only under pressure, embracing a weak testing program.

At the hearing’s start, almost all of the congressmen gushed about the sport, recalling how they collected baseball cards and autographs and naming several retired heroes before leveling their harsh critiques. But with rare exceptions, members of the committee appeared very deferential and unwilling to press the players.

Lawmakers were particularly critical of the plan’s penalties, including a provision allowing for fines instead of suspensions. A first offense could cost a player $10,000 instead of 10 days out from a six-month season.

Using most steroids without a doctor’s prescription for medical purposes is illegal. Baseball banned steroids in September 2002 and began testing for them with penalties in 2004.

Baseball Commissioner Bud Selig sat with arms crossed and lips pursed for much of the hearing. He craned his neck to get a better view as the players spoke.

The wood-paneled hearing room was standing-room only when the players testified, with camera crews lining the walls and clogging the aisles. But much of the crowd cleared out when the players left, leaving empty seats as Mr. Selig began to read his opening statement.

Mr. Selig defended the steroids policy drawn up in January, saying it’s “as good as any in professional sports” and adding that he agreed to shorter bans “on the theory that behavior modification should be the most important goal of our policy.”

Baseball had fought attempts to compel the players to testify, but committee Chairman Tom Davis, a Republican of Virginia, and ranking Democrat Henry Waxman of California threatened to pursue contempt charges if they did not appear.

More than four hours after the hearing began, the players walked in one by one as spectators, lawmakers, and press in the cramped hearing room fell silent.

Curt Schilling, the Boston Red Sox pitcher who’s been outspoken against steroid use, was the first to enter. He sat at one end of the witness table, with Mr. Canseco at the other. Messrs. Palmeiro, Sosa, McGwire and the players’ lawyers were in between.

Mr. Schilling took a shot at Mr. Canseco, saying the former slugger’s claims “should be seen for what they are: an attempt to make money at the expense of others.”