"I've never met that guy, I've never seen him in my life," Bonds said about Arnold. "I've never met him in my life. I've never even heard of the guy -- never."
About Costas, Bonds said: "Is that the story Bob Costas talked about? A little midget man, who doesn't know jack about baseball, who never played the game before? You can tell Bob Costas what I called him."
Bonds, who was not in Wednesday night's lineup after playing all 13 innings in a 7-5 Tuesday night loss to the Braves, declined to address the allegations.
"Don't worry," he said. "My day will come."
Bonds' comments were made to reporters from The Associated Press, New York Post, CBSSportsline.com and MLB.com. The slugger is sitting at 753 homers, two behind the record of 755 set by Hank Aaron.
When those reporters approached his locker, Bonds was watching a clip of the interview on television and then changed the channel to the Dodgers-Astros game.
Arnold told Costas that he had "a very strong feeling" about Bonds' use of steroids "since he [Bonds] was on 'the program.' And like everyone else, 'the program' consisted of 'the clear.'"
Arnold also admitted that he had never met Bonds, but he maintained "the program" as devised by BALCO founder Victor Conte, included steroids. Arnold is widely credited for inventing the then-undetectable substance known as "the clear," which was supposedly distributed to some track and field athletes, plus baseball and football players who were involved with the lab. The clear was later determined to be the performance-enhancing drug THG and is now banned for sale without a prescription.
It is now among a number of anabolic steroids on Major League Baseball's list of banned substances under its Joint Drug and Prevention Policy.
Aside from Bonds' reaction, Arnold's statement unleashed a flurry of denials on Wednesday with even Arnold qualifying his original supposition. Arnold, who had no direct knowledge of what drugs Conte may or may not have given the athletes, told ESPN Radio on Wednesday that his assessment should be viewed only as an opinion, "albeit an informed opinion."
"To me it was always implicit that an athlete that Victor was working with was on 'the program'," Arnold told ESPN Radio.
Conte, who like Arnold, also plea bargained a short sentence that included prison time and house arrest, immediately released his own statement to the New York Times saying that Bonds never used steroids.
"The program I created for Barry was a comprehensive nutritional supplementation regimen and had nothing to do with 'the clear' or any other anabolic steroids," said Conte, who has never implicated Bonds in the scandal, although he said in a television interview that he watched track star Marion Jones inject herself with the performance-enhancing drug under his supervision.
In a subsequent interview with The Los Angeles Times, Conte told the newspaper that he didn't give steroids to Bonds.
"Why would a baseball player have needed an undetectable steroid when drug testing wasn't mandated until 2003?" Conte said. "To suggest that Barry's 2001 record of 73 home runs was assisted by 'the clear' is ridiculous and simply makes no sense."
Baseball didn't begin testing for performance-enhancing drugs at the Major League level until 2003, two years after Bonds set the single-season home run record.
Bonds is among a number of athletes, including Sheffield and the Yankees' Jason Giambi, who were subpoenaed to testify before a federal grand jury in December 2003, only months after the BALCO lab was raided by agents working for the Internal Revenue Service.
Bonds revealed in portions of his testimony illegally leaked to the San Francisco Chronicle that he may have unwittingly used a steroid-based cream or liquid. He and Sheffield have denied taking performance-enhancing drugs, while Giambi is still suffering the fallout of saying that he did.
Another grand jury, the third sitting in San Francisco investigating the BALCO case, is currently trying to determine whether Bonds committed perjury in his original testimony.
Greg Anderson, Bonds' former personal trainer, is one of five BALCO associates who pled to charges after the raid. Anderson served three months in jail, three months under house arrest, and is currently in a Dublin, Calif., prison for refusing to cooperate with the ongoing investigation involving Bonds.
For his part, Bonds usually declines to comment on BALCO, the grand jury and the ongoing controversy.
On Saturday, when asked about the term of the current grand jury being extended for six months, Bonds said firmly: "I'm not discussing it. I haven't been discussing it forever, and I will not discuss it."
On Wednesday, Bonds said he will ultimately talk to Costas about his views. Costas has been a leading commentator who has publicly stated that he believes Bonds used steroids.
"I'll tell him how I feel face-to-face," Bonds said.