With unemployment rates at less than 2 percent in many high-tech fields, the entrepreneurs of Silicon Valley are urging Congress to pass legislation to increase immigration quotas for skilled scientists and engineers from 65,000 today to 115,000 by 2001.

Leaders of high-tech firms say the continued growth of their industry depends upon the availability of more skilled workers from abroad -- since the pool of similarly skilled U.S. workers is insufficient to satisfy demand.

Indeed, immigrants have long played a major role in the founding and development of high-tech firms in the U.S., according to research by Stephen Moore of the Cato Institute.

• About one-third of all scientists and engineers in Silicon Valley were born in a foreign country.

• About one in five of those high-tech firms were founded by immigrants -- employing some 67,500 American workers in 1996 and generating annual revenues of $27.9 billion.

• Just the 10 largest of the firms founded, or co-founded, by immigrants employ 50,000 workers today and account for $20 billion in revenues.

• Although labor unions insist that the firms want to save a few dollars an hour by hiring immigrants rather than native-born workers, analysts point out that it costs firms in the tens of thousands of dollars in legal and regulatory costs to recruit each high-tech immigrant -- a poor bet if saving money is the issue.