WASHINGTON — With the Senate coming back to work, it is scheduled to take up the issue of immigration. And that is what brought Bill Gates to Washington for a rare visit the other day.

The Microsoft billionaire does not love this capital, but he decided to add his personal voice to his Washington office's lobbying effort to expand the number of foreign-born computer scientists allowed to work in this country under a special program known as H1B visas.

In an interview sandwiched between his meetings on Capitol Hill, Gates told me that the "high-skills immigration issue is by far the No. 1 thing" on the Washington agenda for Microsoft and for the electronics industry generally. "This is gigantic for us."

Since autumn 2003, Congress has limited the number of people admitted annually on H1B visas to 65,000. To qualify for such a visa, a person must have at least a bachelor's degree and specialized knowledge and a job offer from an American employer. The visa is generally good for six years, with the possibility of applying for extensions.

So great is the demand for such skills in the burgeoning high-tech world that in August 2005, the last of the visas available for fiscal 2006 were issued. That means a 14-month shutdown of the program, until October of this year.

"It's kind of ironic," Gates told me, "to have somebody graduate from Stanford Computer Science Department and there's not enough H1B visas, so they have to go back to In-dia.... And I have people who have been hired, who are just sitting on the border waiting."

The draft bill that Senate Judiciary Committee Chairman Arlen Specter has been trying to prepare for floor consideration would expand the annual H1B limit to 115,000 from 65,000. By excluding dependents (who now are counted against the cap) from the total, it might mean the entry of as many as 300,000 people a year — one-tenth of 1 percent of the U.S. population.

As Gates said, these are highly paid, highly qualified individuals. Salaries for these jobs at Microsoft start at about $100,000 a year.

Their counterparts can be hired more cheaply in China or India, Gates said, but Microsoft does 85 percent of its R & D work in the United States because it wants its computer scientists interacting directly with its program managers and its marketing people on its own campus.

He said he has a hard time understanding the logic of those who decry the outsourcing of American jobs, yet are reluctant to facilitate bringing the high-skill people who are catalysts for economic growth to this country. "People just shake their heads at what kind of a central planning system would say having 65,000 smart people come in, that's OK, but 70,000 smart people, no."

President Bush and his administration support the expansion of H1B visas. And Gates, in turn, is enthusiastic about the White House and bipartisan congressional efforts to boost the teaching of math and science in American high schools with the long-term goal of expanding the supply of qualified Americans for these jobs.

He is backing that effort both with gifts of technology from the company and grants of $300 million a year from his foundation for innovation in high schools. "But the benefit of things like that has got a fair time lag," he said, "and the next four or five years, it really hangs in the balance: How many of these talented people we want to hire, and who want to come here, can we hire?"

The answer is by no means certain. Opposition to the H1B program grew during the dot-com bust, when groups representing domestic electrical engineers and computer technicians argued that foreigners were taking away their jobs. In 2003, they succeeded in cutting the quota by two-thirds, to 65,000 from 195,000, and they continue to oppose its expansion.

The Bureau of Labor Statistics reports unemployment among computer and mathematical operators is less than 3 percent. Gates said, "If you're graduating from a reasonable university in this country, with a degree in computer science, you have many job offers."

Still, there is reluctance — especially in the House of Representatives — to lift the ceiling on H1B visas in an election year.

The House has responded to public pressure to close the borders to illegal immigration and seems incapable of distinguishing that problem from the value of encouraging high-skill workers to bring their talents to the United States.

That's why Bill Gates comes to Washington.

David Broder is a columnist with the Washington Post.