Every four years, in Washington and concurrently in Cambridge, there is a changing of the guard.

As professors wait for The Call from the president or a cabinet member, department chairs anxiously question their senior faculty members about future plans, and students watch the newspapers and the course catalogues carefully.

With each administration, a few top experts with ties to the right places get on the Delta shuttle and say goodbye to academic life. On their coattails travel junior colleagues and friends, and in their wake sit rudderless graduate students with half-finished theses.

This year, the University saw its usual complement of scholars leave and a few return. Health care, foreign policy, economic and tax choices, welfare reform and labor politics will all see the impact of Harvard minds and Harvard research over the next four years.

Still, there are questions raised by the leap from academia to policy-making, despite the successes of figures such as Henry A. Kissinger '50 and Sen. Daniel Patrick Moynihan.

Politicians and academics both ask if professors, knowledgeable in research, are the right people to actually translate that research into reality. Is it their responsibility to serve their nation when called, or is their proper role in the classroom and at the computer terminal, adding to the store of ideas available to the practitioner?

The contrast between public service and the academic life is fairly clear, even more so when the former professor is in a sexy-sounding field like "intelligence," as is Dillon Professor of International Affairs Joseph S. Nye.

Now chair of the Central Intelligence Agency's National Intelligence Council, the government professor does not quite introduce himself as "Nye, Joseph Nye," on the phone, but his day is emphatically not that of a scholarly recluse.

"Last week I was in Bosnia," he says. "I went to a city where fighting was going on" for a fact-finding mission.

Not all of Harvard's Washington insiders have quite as glamorous a job description as Nye, but most can refer more or less casually to encounters with cabinet-level officials. And all of them share the same complaints and comments about life on the Potomac versus life on the Charles.

The main gripe is the grueling pace and pressure of a hierarchical, high-energy administration compared to the more relaxed lifestyle of most academics.

"Things just happen at warp speed," says Kennedy School Associate Professor of Public Policy John D. Donahue, who has been nominated assistant secretary of labor for policy. "Problems I had weeks to get my mind around at Harvard I have 45 minutes for here."

Others miss the people of Harvard, and lament that they don't even have time to lunch with the numerous Cambridge transplants they are aware of.

"We kind of know we all exist, but we're all too busy to hang out and schmooze," says Danziger Associate Professor of Economics J. Bradford De Long, who is now deputy assistant secretary of the treasury for economic policy. (He adds that he has yet to find an adequate substitute in the nation's capital for Out of Town News.)

But the pulls toward Washington are many, and while they have regrets about students and lost leisure time, the Washington professors are sharing the heady experience of actually doing what many of their colleagues only write and lecture about.