W. Allen Wallis, an economist who became president of the University of Rochester and held a variety of Government posts in Washington, died on Monday at Strong Memorial Hospital in Rochester. He was 85 and lived in Washington.

The cause was a stroke he suffered visiting Rochester, said Helene Snihur of the University of Rochester office of public relations.

Mr. Wallis was the university's president and chief executive from 1962 to 1970 and its chancellor and chief executive from 1970 to 1975, Ms. Snihur said.

A former president, Robert L. Sproull, said that in those 13 years, "Allen Wallis was the principal architect of the University of Rochester as we see it today."

The university, which opened in 1850, is known for the Memorial Art Gallery, the Eastman School of Music, its schools of dentistry and medicine and its library, which is especially strong in the fields of medicine, history and music.

It has 4,400 full-time undergraduates, 2,650 full-time graduate students and 1,010 faculty members.

While he was president, Mr. Wallis began a fund-raising campaign that raised $46.7 million, nearly $10 million more than its original goal, from 1965 to 1968. From 1968 to 1978, the university's extensive expansions and improvements of its physical plant included remodeling the Eastman School and expanding the library and the Medical Center.

From 1962 to 1975, the university's annual budget rose to $200 million from $33 million, its faculty grew by 37 percent, its number of graduate students doubled and its number of undergraduates increased by 45 percent.

From 1975 until he retired from the university in 1982, Mr. Wallis was its chancellor.

Before going to Rochester, Mr. Wallis, who was a statistician as well as an economist, was the dean of the University of Chicago Graduate School of Business from 1956 to 1962. .

As an economist, Mr. Wallis was known for his firm faith in minimal government intervention and in free markets. His writings included the 1976 book "An Overgoverned Society," a collection of his speeches and essays, in which he argued that Government regulations and rules were fettering individual liberties as well as the economy.

He served in the Administrations of four Republican Presidents -- Dwight D. Eisenhower, Richard M. Nixon, Gerald R. Ford and Ronald Reagan -- although he said in 1959, "I'm not actually a Republican." Instead, he said, he was an "independent" or even "apolitical." He also served as a consultant to numerous governmental and business groups.

From 1959 to 1961 he was special assistant to Eisenhower, and concurrently he collaborated with Vice President Nixon on the report of the Cabinet Committee on Price Stability for Economic Growth. In the 1970's, Mr. Wallis served in the Nixon and Ford Administrations as chairman of the President's Commission on Federal Statistics and of the Advisory Council on Social Security.

From 1982 to 1989 he was Under Secretary of State for Economic Affairs, mostly during the Reagan Administration.

George P. Shultz, a Secretary of State in the Reagan years, said Mr. Wallis was "our truth teller."

Much of Mr. Wallis's work as Under Secretary involved international summit meetings. "I relied on him," Mr. Shultz said. "His contributions to our work were immense."

Mr. Wallis was born in Philadelphia, received his bachelor's degree in 1932 from the University of Minnesota and did graduate work there, at the University of Chicago and at Columbia University. He taught at Yale, Columbia and Stanford, and worked in World War II for the United States Office of Scientific Research before joining the University of Chicago business school faculty.

Mr. Wallis was chairman of the Corporation for Public Broadcasting in 1977 and 1978.

His wife of 59 years, the former Anne Armstrong, died in 1994. He is survived by two daughters, Nancy Wallis Ingling of Gambier, Ohio, and Virginia Wallis Cates of Wagon Mound, N.M., and three grandchildren.