Travis Tygart, the senior managing director and general counsel for the United States Anti-Doping Agency, said, “If you’re a player that was using and receiving steroids and other performance-enhancing drugs from Radomski, I think you are pretty nervous right now.”

Mr. Radomski’s home was searched on Dec. 14, 2005, and the federal search warrant affidavit filed in connection with that raid detailed some of his drug transactions. In that raid, federal agents seized “thousands of doses of numerous types of anabolic steroids in both pill and injectable form,” according to a statement from United States Attorney Scott N. Schools, who recently replaced Kevin Ryan, who had overseen the original prosecution of the Balco case.

Obtained in the raid of Mr. Radomski’s home were human growth hormone; insulin growth factor; clomiphene, a fertility drug that can be used as a masking agent; and the steroid Clenbuterol, which was the same drug that the journeyman pitcher Jason Grimsley admitted to using in the search warrant affidavit on his home in Arizona last year.

Federal agents also seized shipping records, financial records, correspondences and contact lists that detailed the distribution of drugs to major league baseball players.

According to the affidavit, an F.B.I. informant set up five transactions with Mr. Radomski, through a mutual acquaintance in baseball. During one conversation between the informant and that baseball source, the source said that if a professional baseball player was currently using performance-enhancing drugs, “then that player likely would be getting it from Kirk Radomski.” The baseball source also called Radomski a “major drug source in professional baseball, who took over after the Balco Laboratories individuals were taken down,” in 2003.

According to the affidavit, Mr. Radomski had accepted personal checks from his clients, but often cashed them instead of depositing them in his account, where they would leave a paper trail. The affidavit listed 23 check transactions with names of current and former Major League Baseball players and their affiliates. Those checks ranged from $200 to $3,500.

Mr. Novitzky wrote that Mr. Radomski was running a cash business, for the most part.

Mr. Radomski’s financial records from 2003 to 2005 were analyzed. Major League Baseball did not have a steroid testing policy until 2003 and did not suspend any players for a positive test until 2005. Since then, 15 major leaguers have been suspended for violating the drug policy.