WASHINGTON, Sept. 7 (Bloomberg News) — The House approved the most sweeping changes to United States patent law in more than half a century on Friday in a victory for computer companies like Microsoft and finance companies like Goldman Sachs.

The legislation, approved 220 to 175, would make patents harder to obtain and easier to challenge and is intended to curtail litigation by limiting where patent owners can file suit and how much they can collect in damages.

Approval came after last-minute changes to appease critics, including labor groups, universities, the Bush administration and the drug maker Pfizer, which said the original proposal went too far in weakening patent rights and might hurt investment in new technologies and cost American jobs.

Even with the changes, the measure faced opposition from manufacturers, including Caterpillar, Eli Lilly and Procter & Gamble. Opponents said the measure favored certain industries over others.

“It is a horror story for American inventors and a windfall for thieves,” said Representative Dana Rohrabacher, Republican of California. “Foreign and domestic technology thieves are licking their chops.”

Intense lobbying has surrounded the issue, reflecting the importance of patents to the American economy. Intellectual property in the United States, dominated by patents, is valued at as much as $5.5 trillion, more than 40 percent of the nation’s gross domestic product, according to a 2005 study by USA for Innovation, a Washington group that advocates free trade.

Microsoft, Intel and Cisco Systems have been lobbying for changes for more than five years. They say they have been under siege from lawsuits seeking high royalties on small features.

The companies are subjected to “legalized extortion,” said one sponsor of the measure, Representative Lamar Smith, Republican of Texas. “Too many patents of questionable integrity have been approved, and owners of these patents have found a unique way to make money.” (What are these and who says they are questionable.? Maybe they are questionable to Microsoft who stole them!)

The two chambers of Congress started with identical proposals in April, and the Senate version may come to a vote this year.

The measure passed by the House would change the rules at the Patent and Trademark Office so patents would go to the first person to file an application, not necessarily the first inventor. That would limit years-long disputes over who was the first to invent new technology and would bring the United States in line with other countries’ patent rules. It would also allow third parties to introduce evidence against applications and would create a system, called post-grant opposition, to challenge new patents.

In litigation, it would limit where patent suits could be filed so that cases are not concentrated in court districts deemed favorable to plaintiffs, create a new way to calculate damages to reflect the contribution of the invention to the overall product and allow immediate appeals of court rulings on the interpretation of patent terms while cases are proceeding.