An initial disparity, even if known to the employee, might be small, Justice Ginsburg said, leading an employee, particularly a woman or a member of a minority group “trying to succeed in a nontraditional environment” to avoid “making waves.” Justice Ginsburg noted that even a small differential “will expand exponentially over an employee’s working life if raises are set as a percentage of prior pay.”

Justices John Paul Stevens, David H. Souter and Stephen G. Breyer joined the dissent.

Ms. Ledbetter’s salary was initially the same as that of her male colleagues. But over time, as she received smaller raises, a substantial disparity grew. By the time she brought suit in 1998, her salary fell short by as much as 40 percent; she was making $3,727 a month, while the lowest-paid man was making $4,286.

A jury in Federal District Court in Birmingham, Ala., awarded her more than $3 million in back pay and compensatory and punitive damages, which the trial judge reduced to $360,000. But the United States Court of Appeals for the 11th Circuit, in Atlanta, erased the verdict entirely, ruling that because Ms. Ledbetter could not show that she was the victim of intentional discrimination during the 180 days before she filed her complaint, she had not suffered an “unlawful employment practice” to which Title VII applied.

Several other federal appeals courts had accepted the employment commission’s more relaxed view of the 180-day requirement. The justices accepted Ms. Ledbetter’s appeal, Ledbetter v. Goodyear Tire and Rubber Company, No. 05-1074, to resolve the conflict.

Title VII’s prohibition of workplace discrimination applies not just to pay but also to specific actions like refusal to hire or promote, denial of a desired transfer and dismissal. Justice Ginsburg argued in her dissenting opinion that while these “singular discrete acts” are readily apparent to an employee who can then make a timely complaint, pay discrimination often presents a more ambiguous picture. She said the court should treat a pay claim as it treated a claim for a “hostile work environment” in a 2002 decision, permitting a charge to be filed “based on the cumulative effect of individual acts.”

In response, Justice Alito dismissed this as a “policy argument” with “no support in the statute.”

As with an abortion ruling last month, this decision showed the impact of Justice Alito’s presence on the court. Justice Sandra Day O’Connor, whom he succeeded, would almost certainly have voted the other way, bringing the opposite outcome.

The impact of the decision on women may be somewhat limited by the availability of another federal law against sex discrimination in the workplace, the Equal Pay Act, which does not contain the 180-day requirement. Ms. Ledbetter initially included an Equal Pay Act complaint, but did not pursue it. That law has additional procedural hurdles and a low damage cap that excludes punitive damages. It does not cover discrimination on the basis of race or Title VII’s other protected categories.

In her opinion, Justice Ginsburg invited Congress to overturn the decision, as it did 15 years ago with a series of Supreme Court rulings on civil rights. “Once again, the ball is in Congress’s court,” she said. Within hours, Senator Hillary Rodham Clinton of New York, who is seeking the Democratic nomination, announced her intention to submit such a bill.