The Supreme Court, in an important victory for women's rights advocates, yesterday opened a new era of employment discrimination lawsuits on comparable pay between men and women.

In a 5-to-4 ruling, the justices allowed jail matrons in Oregon to sue for sex discrimination because they were paid less than male guards, even though the jobs were not identical.

Before yesterday's decision, the only sure grounds for a pay discrimination claim by a woman under federal law was "unequal pay for equal work" -- an allegation that she was paid less than a man holding an identical job. The jail matrons and women's rights lawyers said that lower pay for a comparable, if not equal, job could also be the basis for a sex discrimination charge.

The justices did not specifically approve such suits yesterday and Justice William J. Brennan, Jr., who wrote the opinion, took pains to say the holding was a narrow one. But the court rejected the pleas of employers to ban them outright in order to prevent a flood of litigation. Both sides in the "comparable worth" controversy agreed yesterday that the flood may now begin, Brennan's comments notwithstanding, and that the door is now open for the concept of comparable worth.

The controversy stems from a suit filed by four jail matrons who guarded women prisoners at the Washington County, Oregon, jail, and were paid roughly $200 less per month than the men who guarded male prisoners. They were also paid less than the county's job evaluation study suggested the women should be paid. But the men supervised more than 10 times as many prisoners per guard than the females and the women also spent time on less physically demanding clerical duties.

A U.S. District Court held that the jobs were not equal. Under federal law, the judge ruled, the court could consider only claims of lesser pay for equal work. The Ninth U.S. Circuit Court of Appeals reversed the lower court.

At issue were two laws: the Equal Pay Act of 1963 and the Civil Rights Act of 1964. The first specifically prohibits unequal pay for identical jobs and at the same time defines what is not discrimination, for example, lower wages dictated by a merit or senority system or a gap in pay "based on any other factor other than sex." The second law is a general prohibition against sex discrimination in employment. Through an amendment to the Civil Rights Act -- the Bennett Amendment -- Congress sought to make the two laws complementary.

The women brought suit under Title VII of the second law, the Civil Rights Act. The dispute centered around that tie-in. Employers, in this case and several other major cases still pending, argued that the amendment restricted the Civil Rights Act's application to equal pay for equal work as defined in the Equal Pay Act.

Brennan said yesterday that the Bennett Amendment did not restrict the civil rights law. Congress, he said, has indicated that a "'broad approach' to the definition of equal employment opportunity is essential to overcoming and undoing the effect of discrimination. . . . We must therefore avoid interpretations of Title VII that deprive victims of discrimination of a remedy, without clear congressional mandate."

He noted the concern of employers that "comparable worth" lawsuits would allow courts to examine and, if required, restructure a company's entire compensation scale. But he said this was not a "comparable worth" suit. Instead, he said, the possible discrimination occurred because Washington County paid the jail matrons less than the county's job evaluation called for.

But it was Brennan's broad approach to the Title VII issue that women's rights lawyers saw as a victory, allowing it to be used for compensation complaints beyond "equal pay for equal work." The style of the ruling was compared by some observers to the Bakke decision on affirmative action, which was equally indirect. In failing to foreclose the use of race as a factor, Bakke allowed courts across the country to uphold affirmative-action plans.

Justice William H. Rehnquist dissented in County of Washington v. Alberta Gunther yesterday and was joined by Chief Justice Warren E. Burger and Justices Potter Stewart and Lewis F. Powell Jr.