When the Justice Department held its annual awards ceremony a few weeks ago, the winners of the $1,000 distinguished service prizes included an undercover FBI agent and prosecutor from the Abscam investigation, an undercover drug enforcement agent who busted a huge marijuana ring, another FBI agent who exposed organized crime figures on the New York waterfront, and Ernest J. Brown of the tax division.

There among the young investigators was an old professor. Brown is a recognized scholar in the tax field, who started a new career at the Justice Department 10 years ago after retiring from his job as a professor at Harvard Law School. Now 75, Brown was recognized for his work in winning appeals that saved the government $1 billion on a complicated gas excise cas involving the Virgin Islands and Puerto Rico and another that led to an $18.5 million settlement on a longstanding case by International Telephone and Telegraph Corp.

"I felt in strange company," Brown said the other day, recalling the ceremony as he sat in his cluttered office surrounded by book shelves groaning with tax tomes. He is more at ease, he said, arguing the merits of something like whether ITT's stock exchange with Hartford Fire Insurance Co. in the late 1960s qualified as a nontaxable reorganization.

Brown said he taught a seminar on corporate reorganization and taxation for 25 years and enjoyed a chance to practice his teachings in court. How is the courtroom different from the classroom? "You have to use a different tone of voice talking to the three 'students' on the bench [the usual court of appeals panel]. You can't say, 'That's a foolish question,'" he said with a smile.

In some cases, the appellate judges really were Brown's students, a fact that might give the government a psychological advantage, according to Carr M. Ferguson, head of the tax division during the Carter administration. But, Ferguson added, "He re-earns that respect every time he argues a case."

In the last administration, Ferguson said, Brown would sit in on weekly meetings with the government's top tax attorneys that included two former students, the commissioner of the Internal Revenue Service and the assistant secretary of the treasury for tax policy.

"Ernest really has been a tremendous resource for the United States over the last 10 years," Ferguson said. "He achieved reversals of complex, potentially very harmful lower court opinions that would have been very difficult for the government to live with. He's been a great teacher for a decade of young tax division attorneys and he takes on a workload that would exhaust men several decades younger. The law is his life."

John F. Murray, now acting head of the taxdivision, and Gilbert E. Andrews, a deputy who was Brown's supervisor, joined in the praise. "He's a real delight and a great scholar, the guy we threw the tough cases to," Murray said. "I'm one of his chief appreciators and fans," Andrews said. "He's one of the government's heavy guns in tax litigation."

Andrews also recalled one Christmas season when a government brief was due in Philadelphia and had to be hand-carried because it was too late for the mails.

"Ernie took it up there by train so someone with a family wouldn't have to. He was willing to take on menial duties." Andrews said it was particularly exciting to watch Brown grow in his new job, in his late 60s and into his 70s. Why doesn't he retire?

"My sister asks me that all the time," Brown said with a smile. "What else would I do? I still enjoy my work." CAPTION: Picture, Ernest J. Brown of Justice Department's tax division, winner of $1,000 distinguished service award and tireless worker. By James M. Thresher -- The Washington Post