In John G. Roberts Jr., many of the corporate chieftains who helped put President Bush in the White House see a Supreme Court nominee with whom they can do business. That's partly because so many of them already have.

As one of Washington's most sought-after appeals court practitioners, Roberts, the son of a Bethlehem Steel Co. executive, advocated on behalf of some of the biggest names in business while practicing at Washington's biggest law firm, Hogan & Hartson LLP.

His clients included everyone from carmakers Toyota and Chrysler to trade groups such as the National Mining Association and the U.S. Chamber of Commerce.

Not since Lewis F. Powell Jr., a friend to the chamber who retired from the court in 1987, has there been a nominee with as much career experience navigating the legal complexities of the business world.

That distinction - combined with some of his opinions on the federal bench that question federal regulatory powers - has critics worried that Roberts will seek to roll back a wide range of environmental and workplace regulations that tend to favor the less powerful.

But it buoys some in the business lobby as they look to the courts for help in a post-Enron era of increasing Securities and Exchange Commission regulations and blockbuster class-action lawsuits.

"Everything instinctively tells me that he understands their needs and their issues ... and I think in general the business community has good reason to be optimistic by having John on the court," said Carter G. Phillips, an appellate lawyer who regularly argues Supreme Court cases and knows Roberts professionally.

Legal experts say Roberts' biggest help to the business community might be in using his influence as a junior justice to get their cases on the docket. The court has routinely disappointed business advocates in recent years by studiously refusing to hear cases involving issues they consider paramount.

"I've got to believe John is more likely to be interested in hearing business issues than the other judges," Phillips said. " ... You will have a more sympathetic ear to the idea of taking some of the business cases that are important."

Business leaders vetting potential nominees in the weeks before Bush's decision were looking for someone who could live up to the legacy of retiring Justice Sandra Day O'Connor, who affirmed business interests in at least two respects. She favored limited punitive damage awards to plaintiffs suing corporations. Her tendency to support the pre-eminence of federal regulation often relieved businesses of the burden of coping with a patchwork of state laws.

Roberts soon seemed a fine choice in corporate circles, though at Hogan & Hartson he often argued on both sides of business-related issues. His experience before the Supreme Court covered antitrust, consumer law, environmental law, interstate commerce and a wide range of other topics originating with boardroom disputes.

"It's not like he sprang from the head of Zeus," said Hank Cox, a spokesman for the National Association of Manufacturers. "He has a record, and at first blush, he looks like a guy we could get behind, but I don't want to prejudge."

The manufacturers group and the U.S. Chamber of Commerce are among a group of business lobbies that have pledged to get more politically involved in federal court appointments, arguing that it would be a mistake to let right-wing evangelicals and liberal groups define the debate.

Former Michigan Gov. John Engler, a Republican who heads the manufacturers association, has been leading the charge. His group formed a committee, which met yesterday, to look at the nomination and make a recommendation.

For now, the chamber is staying quiet, saying it wants to take its time scouring Roberts' background before speaking out. However, Roberts is well known to the group, having filed a friend-of-the-court brief on its behalf in a case that involved federal pre-emption of state law. He also has been a panelist on the chamber's moot court program set up to help train appellate lawyers. The chamber is mulling an advertising campaign on Roberts' behalf during the nomination battle.

But legal experts and business advocates say trying to discern Roberts' judicial philosophy from his corporate legal work is risky, since most attorneys for hire are paid to take their clients' position. With a lengthy client list built up over a decade, Roberts has been on both sides of issues including states' rights vs. federal authority, consumer protection vs. government regulation and developers vs. environmentalists.

In a major victory for business, Roberts argued before the Supreme Court in 2001 that a Toyota employee who could no longer do her job because of carpal tunnel syndrome was not covered under the Americans with Disabilities Act. The court unanimously took his position, ruling that the act does not necessarily cover someone who is unable to perform certain work functions but is otherwise able to brush her teeth, wash her face, tend a garden and manage other tasks in daily life. The decision was written by O'Connor, whom Roberts seeks to replace.

But Roberts hasn't always been on the side of big business. He represented state prosecutors in their antitrust case against Microsoft Corp., a particularly complicated litigation that dealt with the software giant's monopoly power.

His record with environmental cases is equally diverse. In a case heard by the U.S. Court of Appeals for the Fourth Circuit in Richmond, Va., he argued for the National Mining Association in a dispute between environmentalists and the state of West Virginia over permits the state granted for so-called "mountaintop removal" coal mining. The court ruled for various reasons that the dispute didn't belong in federal court, handing environmentalists a bitter defeat.