Benjamin V. Cohen, 88, a brilliant and scholarly lawyer who played a principal role in creating the New Deal legislation that reshaped American government and industry during the administration of Franklin D. Roosevelt, died yesterday at Georgetown University Hospital.

The cause of death was listed as pneumonia.

Mr. Cohen was one of the last survivors of the circle of presidential aides and advisers, formal and informal, who were commonly known as Roosevelt's Brain Trust. A modest and self-effacing man, he continued to live quietly here, advising and consulting, long after he formally left government service.

In addition to playing an essential part in creating domestic policy to cope with the Depression, Mr. Cohen was regarded as the intellectual leader of those administration lawyers who, as the 1930s ended and war loomed in Europe, sought to find ways to prepare this country for the expected onslaught of the dictators.

Inspired by FDR's election in 1932 at a time of social despair and economic chaos, Mr. Cohen and the man with whom he formed a celebrated and prolific partnership, Thomas G. Corcoran, joined the new administration at its start and played vital roles in its legendary first 100 days.

They, and the many young lawyers who joined them as colleagues, arrived at a time when the nation was still reeling from the effects of the Wall Street Crash of 1929.

From their minds and pens, set feverishly to work during all-night drafting sessions, came the shape and structure and the paragraphs and clauses of legislation designed to bring order to the nation's money markets and ultimately to create new confidence in the American financial system.

While holding a variety of relatively obscure government posts, Mr. Cohen and Corcoran, who died in 1981, were credited with writing in large measure or in toto such pivotal New Deal measures as the Securities and Exchange Act, the original Wage and Hour bill and the Public Utilities Holding Company Act.

Described by his admirers as visionary and idealistic, Mr. Cohen also was regarded, even by those who sought to overturn his legislation in the courts, as a legal draftsman of unmatched gifts.

Although said to be of shy and retiring demeanor, Mr. Cohen proved as skillful in arguing for his bills as he was in drafting them. The Utilities Holding Company Act, in particular, was vigorously opposed by determined foes. It survived every challenge and was regarded as a personal triumph for its author.

"In my judgment he was the greatest public interest lawyer who ever lived," Joseph L. Rauh Jr., a New Deal disciple and colleague, said last night. "He thought not in terms of himself or of politics, but of what was best for the most," Rauh said.

"He is the high priest," Corcoran said of him a few years ago. "He is the saint."

Mr. Cohen's roles as assistant and adviser, and his humility made it unlikely that he would receive full credit for all his accomplishments. Many were best known to his friends and close associates.

In 1969, at a 75th birthday party held for Mr. Cohen, Corcoran tried to sum up his friend's achievements. "Ben was in substance our economic administrator during the war," Corcoran said. "The whole structure of wage and price controls was his work . . . .

"Lend-Lease was his.

"He kept the civilian economy on a noninflation basis all through the war."

Mr. Cohen also is credited with being the architect of the famed exchange of aging American destroyers for British bases in the Western Hemisphere that allowed Britain to survive in the Battle of the Atlantic in the dark early days of World War II.

Benjamin Victor Cohen was born on Sept. 23, 1894, in Muncie, Ind., where his father, who had emigrated from Poland, operated a business. He held undergraduate and law degrees from the University of Chicago, where one of his professors called him "the most brilliant student I have ever taught."

He also did graduate work in law, during which he came under the influence of Felix Frankfurter. He later worked as a law clerk for a federal appeals court judge, and during World War I was an attorney for the U.S. Shipping Board. Poor eyesight caused his rejection from military service.

After the war he represented American Zionists at the Paris Peace Conference. Afterward, he practiced law in New York, specializing in corporate reorganization.

In 1933, he was in the vanguard of the phalanx of young lawyers who at the urging of Frankfurter, their mentor and teacher, came here to join the new Roosevelt administration.

At the outset, he lived along with Corcoran and other lawyers in a house in Georgetown that despite its occupants' early passion for anonymity, became known in political gossip as "the little red house in R Street."

There and in quarters the two later took elsewhere in the city, Mr. Cohen's diligence and industry were demonstrated, as they held night-long drafting sessions to remove objections voiced during the day by those opposed to or skeptical of their bills.

"Whatever he did, he did thoroughly," said another New Deal disciple and associate, Washington lawyer David Ginsburg. "When he went into a problem, he understood it."

As Mr. Cohen's interests began to incline toward foreign affairs, he went in 1941 to London as legal adviser to the U.S. ambassador. On his return, he served as general counsel to James F. Byrnes in the Office of Economic Stabilization. After Byrnes became secretary of state, Mr. Cohen became his special assistant. Later he was appointed State Department counselor.

He left the government in 1947, but was later named a delegate to the United Nations.

His years in retirement, were spent, according to Ginsburg, in "consulting with friends, in government, on the hill . . . in the administration. Whatever the administration, he was a man who was available for advice.

"His telephone would be ringing all the time," Ginsburg said.

"He was the last of a generation."

Survivors include a sister, Pearl C. Freund, of Los Angeles.