Eugene V. Rostow, 89, a lawyer and influential law school dean who also played an important role in and out of government as a shaper of national policy on issues of war and peace, nuclear weapons and Vietnam, died yesterday in Alexandria.

A son, Nicholas Rostow, said that his father died of congestive heart failure at the Sunrise assisted-living facility.

Through World War II and the Cold War that followed, Mr. Rostow was regarded as standing in the front rank of the corps of brilliant intellectuals who moved between the nation's universities -- law schools in particular -- and government service.

At Yale University, he was regarded as one of the law school's great deans, serving from 1955 until 1965 and credited with revamping the curriculum and helping the institution reach the prominent position it enjoys today.

At the same time, although he did not seek out office in Washington, according to another son, Victor Rostow, "he would want to be remembered as someone who was always available to serve his country." A Democrat who believed in a strong defense and firmness in foreign affairs, he knew his share of controversy.

An adviser to the State Department in the early 1940s and again in the early 1960s, he became No. 3 official in the State Department as undersecretary for political affairs in 1966, when the nation's involvement in Vietnam was deepening under President Lyndon B. Johnson. During the early part of President Ronald Reagan's administration, he served for a turbulent period as head of the Arms Control and Disarmament Agency.

"He always said, 'You never refuse your president,' and he was always proud" of his years in government service, Victor Rostow said.

The son said his father helped define the nation's obligations in Vietnam.

"I think he saw our treaty obligations as the fundamental principle," Victor Rostow said. "Beyond that, he also believed that if we could establish a breathing space for South Vietnam that they would govern themselves in a manner that would be a good deal more pleasant and effective for the people of Vietnam than what transpired."

In the 1970s and 1980s, through his writing and speeches and as a leader of the Committee on the Present Danger, Mr. Rostow contributed to the national debate over foreign and nuclear policy. Known as a neoconservative, he accepted a Reagan administration offer early in 1981 to head the arms control agency.

Infighting between the administration and congressional hard-liners appeared to erode his support, and after about two years, he was dismissed. At the time, he was described in an editorial in The Washington Post as someone who brought to the capital "a strong, defense-minded conservatism."

The same piece also viewed him as a "somewhat old-fashioned spokesman for international rectitude."

Washington lawyer Paul Stevens, former chairman of the American Bar Association's standing committee on law and national security, recalled Mr. Rostow as someone who tried to call attention in the late 1970s and early 1980s to a need to rebuild the nation's defenses and to take a strong stand against what was then Soviet-led communism.

The ABA committee presented Mr. Rostow with an award for his "extraordinary contributions," Stevens said.

Stevens added that Mr. Rostow was admired by both Democrats and Republicans "not only for his brilliance," but also for his principles and integrity.

Mr. Rostow was born in Brooklyn, N.Y., on Aug. 25, 1913. He was raised in New Haven, Conn., and graduated from Yale in 1933 as a member of Phi Beta Kappa. He then studied economics, an area in which he was to demonstrate major academic interest, at King's College, which is part of England's Cambridge University.

After returning to this country, he studied at Yale Law School, where he was editor of the Yale Law Journal. He practiced briefly with a major Wall Street law firm and then joined the Yale law faculty in 1938. He became a full professor six years later.

Much of his scholarship and a good deal of his prolific writing concerned interactions among economics, philosophy and the law. One of his early books was "Planning for Freedom: The Public Law of American Capitalism."

He took a leave of absence from Yale during World War II to serve in this country and abroad as an official of the Lend-Lease Administration, dealing with problems of providing supplies to America's allies.

"He thought of himself first as a teacher and second as a public servant," Victor Rostow said, and instilled in his children the belief that "if you can't serve your country in the military, you must serve in the government."

Mr. Rostow was described by his son Nicholas, counselor to the U.S. Mission to the United Nations, as a courageous figure who spoke out against injustice when he saw it.

His 1945 article in the Yale Law Journal was credited with a key role in prompting efforts to make restitution to Japanese-Americans interned during World War II. In 1961 he called on lawyers to take a more vigorous role in enforcing the Constitutional rights of black Americans.

In 1955, when Mr. Rostow became dean of Yale Law School, the Ford Foundation announced a $1.6 million grant to help the school carry out a major curriculum revision.

The new course of study created under Mr. Rostow's leadership focused on the associations between law and other important academic disciplines, including history, economics and sociology. More seminars were offered, along with more opportunities for independent research. The doctrine developed is often called legal realism; Mr. Rostow preferred "legal idealism." It has been credited with helping produce a crop of public spirited lawyers eager to take part in public affairs.

"We remain convinced," Mr. Rostow once said, that "that kind of humane and broadly based law school training is indispensable" in preparing lawyers not merely as advocates "but as participants in every phase of their work in the endless struggle to achieve justice through law."

In a statement released last night, Anthony Kronman, current dean of the 178-year-old institution, called Mr. Rostow "one of the Law School's great deans" and said that "much of the Yale Law School we now know -- to which we have become so accustomed . . . was built or rebuilt during Gene's deanship years."

Mr. Rostow was Sterling professor emeritus of law and public affairs at Yale.

In addition to his sons, survivors include his wife, the former Edna Greenberg, of Alexandria, to whom he was married for 69 years; a daughter, Jessica, of New Haven; two brothers, former National Security Adviser Walt Whitman Rostow of Austin and Ralph Emerson Rostow of Sarasota, Fla.; and six grandchildren.

Regarded as one of its greatest deans, Eugene Rostow overhauled the curriculum at Yale Law School.