Alberta Gunther, a schoolmarmish matron at the county jail in Hillsboro, Ore., never dreamed she was lighting the fuse on a Supreme Court case when she sued her boss for wages equal to what the male guards were getting.

She thought it was just a case of ordinary discrimination: "They got paid a hell of a lot more and it wasn't fair. That's all."

But the jobs were not exactly equal. Males guarded male prisoners; she guarded women and there were fewer of them. Unlike the men, she spent a lot of time doing clerical work, cooking and scrubbing.

These differences carried her case from the familiar turf of equal pay for equal work into the uncharted battleground of "equal pay for work of comparable worth," and the combatants are rolling out the heavy artillery.

Pay equity has been called "the civil rights issue of the '80s." Legal experts hope the Supreme Court decision in Alberta Gunther's case will provide a definitive thumbs up or down on whether the nation's existing antidiscrimination law extends, at all, to jobs that are comparable as well as to those that are identical. If the court says yes, then the law can be used by women to attack the persistent earnings gap with men by taking employers to court. The exact reach of the comparable-worth doctrine would then have to be spelled out case by case.

At the other possible extreme, if the court issues a decisive enough no, then employers could pay women less than men and not be liable under sex discrimination law, except in cases of exactly "equal work," attorneys said. The fight would then be focused in arenas other than the courts, such as collective bargaining and a push for new legislation.

A decision is expected by the end of the current court term, around the end of June.

Business groups, government officials and others who strongly oppose the idea of "comparable worth" argue that it could completely upset the economy, cost employers -- public and private -- billions in payroll dollars and legal fees, and put courts and bureaucrats in the business of setting wage rates. Moreover, they say, no workable definition of comparable worth exists.

The issue is "so incredibly complicated, it should be a matter of legislative policy . . . We're fairly firm on that," said John Tysse of the United States Chamber of Commerce.

Supporters of the idea agree that it is radical -- and difficult. It tackles society's ingrained notions of "women's work," which has traditionally been valued lower than "men's work," and it raises questions about how employers and "the market" reward various kinds of labor. But no advance in civil rights has been free of costs and pain, the idea's backers argue.

Economic pressures have broadened support for the concept of comparable worth, according to some advocates. "Contrary to popular belief, a lot of men support this, too," said William Callahan, leader of a public employes' union in San Jose, Calif., where a conflict over comparable worth has had city workers on the verge of a historic strike."We see more and more two-paycheck families. Only they're really one-and-a-half-paycheck families."

The practical difficulties of comparing occupational apples and oranges are undeniable. Eleanor Holmes Norton, head of the Equal Employment Opportunity Commission in the Carter administration and a leading proponent of comparable worth, described it as "the most difficult ever to arise" under the civil rights banner.

Proponents contend that employers should require no complicated definitions of job comparability to help them recognize some of the obvious inequities. According to Marilyn Depoy, of the giant American Federation of State, County and Municipal Employes (AFSCME), "When a person whose job requires a college education makes less than what is basically a common laborer, there's something wrong. You know'em when you see 'em."

Despite decades of social change, women who work fulltime still earn only about 60 cents for every dollar earned by men. Female college graduates earn an average of $13,395, barely more than the earnings of men with only eight years of elementary school education ($12,965) and less than men with only three years of high school, according to the most recent Census Bureau figures.

Half of all working women remain in secretarial, teaching and other fields that are predominantly (at least 70 percent) female. And the Equal Pay Act, passed in 1963, doesn't help them much. Its provisions are limited to ensuring, for example, that a company's male secretaries are paid no differently than female secretaries at the same level.

Despite increases in the number of females in higher-paying business and professional jobs, according to analysts in the Women's Bureau of the Labor Department, two main factors have maintained the earnings gap. One is the concentration of women in traditionally "female" jobs. The other is the dramatic increase in the last two decades in the proportion of women who work (from 37 to 50 percent), which has meant that a higher percentage are in beginner status, concentrated in or near entry levels. But even after adjusting for these and other factors such as the fewer years of working life averaged by women, the analysts conclude, much of the earnings difference remains unexplained.

The pay-equity controversy flames hottest when a traditional female job is compared with a male job totally different but arguably of about the same value to the employer in terms of skill and responsibility. Advocates compare, for example, male liquor store clerks in Montgomery County, who get a starting salary of $13,500 a year, with beginning librarians, who tend to be women and are paid $11,000.

Even in fields where there is a labor shortage, as in secretarial work currently, women's salaries remain depressed, said Day Piercy, director of the Chicago-based Women Employed, one of the most active groups pushing the comparable-worth concept. "Prejudices about women's work keep the market down."

Although the immediate legal issue is sex discrimination, comparable worth could acquire a broader application -- not only to male-female pay differentials, but to black-white, blue collar vs. white collar, or any number of perceived inequities. In some cases where pay scales have been revised on a point system, men as well as women have had their pay raised.

So far, the courts have split in four major appeals cases in which women have sued for equal pay for work of what they considered to be comparable value under the existing sex discrimination law, Title 7 of the Civil Rights Act.

Women at a Westinghouse light bulb plant were paid less than men, even when the company, using a point system, rated their jobs equal in skill and responsiblity, according to the International Union of Electrical, Radio and Machine Workers (IUE). An appeals court ruled against the company.

But in another case, city nurses in Denver, most of whom are women whose starting salaries ($1,064 a month) were less than those of male tree trimmers ($1,164) and painters ($1,191), failed in their appeal. The court affirmed a ruling by U.S. District Judge Fred Winner that the suit was "pregnant with the possibility of disrupting the entire economic system of the United States of America."

If the Supreme Court's decision in the Gunther case closes the door on comparable-worth litigation, women's groups, labor unions and other advocates are geared up on other fronts.

In San Jose, Calif. the public employes union, AFSCME, backed by the AFL-CIO, came close to striking over the issue of comparable worth. San Jose's mayor, a woman, has expressed support for the concept. But the union will stop work if an agreement isn't reached by the July 5 contract deadline, according to union business agent Callahan.

Some 1,500 city employes, mostly women, would get raises costing, $3.2 million over a four-year period if present inequities are corrected, according to a job analysis by an outside consultant hired by the city, he said.

"If we reach an agreement on comparable worth, it would be historic, the first one," and it would affect all the area's wages, said Callahan. "If our clerical workers' wages are adjusted dramatically upward, private employers will have to adjust, too."

Advocates acknowledged, however, that they would have to "pick their shots" to some extent. "We wouldn't go into Detroit right now to talk about this," said AFSCME's Depoy. "Where the existence of essential services is on the line, you have to be realistic."

A number of states are considering pay equity legislation, including California, Connecticut, New Jersey, Georgia and Oklahoma. The California proposal could, by one estimate, raise the pay of 80,000 female state workers at a cost of $120 million per year. Idaho has already enacted a law that bases public pay on points related to skills and responsibility, raising the pay of more than 2,000 clerical workers by around 16 percent.

Alberta Gunther, meanwhile, has gone to work in a neighboring county (metropolitan Portland), where she says the sheriff pays male guards and female matrons the same. She was dismissed from her former job after she and three other matrons filed their lawsuit.

Now 47, she had worked as an elementary school teacher until she found herself unemployed and answered an ad for the jail matron's job. She and her husband, a salesman of janitorial supplies, have five children.

"My lawyer tells me we're getting pretty famous," she said of the Supreme Court case. "But I'd rather have the money."