A little over three years after Pan Am Flight 103 blew up over Lockerbie, Scotland, Fred D. Thompson provided advice to a colleague about one of his law firm’s new clients: The man representing the two Libyan intelligence officials charged in the terrorist bombing.

The colleague, John Culver, a partner at the Washington firm of Arent Fox Kintner Plotkin & Kahn began advising the two suspects’ Libyan lawyer in February 1992. Mr. Thompson, according to a memorandum from that era written by his secretary, held “discussions with Culver re: Libya” that same month.

At the time, Libya was facing international outrage for refusing to comply with a United Nations demand that the two suspects be extradited to the West for trial in the 1988 bombing, which killed 270 people. Revelations that American firms were representing Libyan interests provoked a furor among the Pan Am victims’ families. Some law firms refused to represent the country or the suspects, while others withdrew.

The involvement of Mr. Thompson, who worked part-time for Arent Fox as a lawyer and lobbyist from 1991 until shortly before his election to the Senate in 1994, never became public. But Arent Fox’s chairman, Marc L. Fleischaker, confirmed that Mr. Thompson, who is now seeking the Republican presidential nomination, briefly provided Mr. Culver with advice about the suspects’ case, billing the firm for 3.3 hours of his time.