The 5-4 decision underscored a provision in a federal civil rights law that sets a 180-day deadline for employees to claim they are being paid less because of their race, sex, religion or national origin.

Without a deadline, Justice Samuel Alito wrote for the court, employers would find it difficult to defend against claims ''arising from employment decisions that are long past.''

Justice Ruth Bader Ginsburg, writing in dissent for the court's liberal members, urged Congress to amend the law to correct the court's ''parsimonious reading'' of it.

Lilly Ledbetter, a longtime supervisor at Goodyear Tire & Rubber Co.'s plant in Gadsden, Ala., said sex discrimination was behind a series of decisions that left her pay significantly below that of men who performed similar work.

After 19 years with Goodyear, Ledbetter was making $45,000 a year, $6,500 less than the lowest-paid male supervisor. The company said poor performance evaluations, not discrimination, were behind Ledbetter's salary. She retired in 1998, shortly after claiming discrimination.

A jury sided with Ledbetter, but an appeals court overturned the verdict because she had waited too long to begin her lawsuit.

The Supreme Court agreed that workers who wait too long under the civil rights law are out of luck. Alito said that ''the passage of time may seriously diminish the ability of the parties and the fact-finder to reconstruct what actually happened.''