The plaintiffs include a pair of senior citizens, worried about being separated in a nursing home. There are working mothers and fathers concerned about their children's health insurance. Others describe immigration, adoption and inheritance woes.

The nine same-sex couples and one bereaved gay man who are suing Maryland for the right to marry say they are not asking for creation of a new right, just the chance to share in one that has been fundamental for heterosexuals.

"I think the thing that binds us all is that we want a level playing field for our families, to have the same protection that other families have," said Baltimore engineer Lisa Polyak, who with teacher Gita Deane, her partner of 24 years, is raising two daughters.

The suit, filed on their behalf by the American Civil Liberties Union, was argued in Baltimore Circuit Court on Tuesday before Judge M. Brooke Murdock. The ACLU is asking the court to strike down a 1973 state law that limits marriage to heterosexual couples. Defendants are court clerks in the state to whom the gay couples unsuccessfully applied for marriage licenses.

"The exclusion of same-sex couples from marriage is totally irrational," attorney Kenneth Y. Choe of the ACLU told Murdock.

Attorneys for the state were quick to defend Maryland law and years of precedent.

"Marriage is described as between a man and a woman repeatedly," argued Assistant Attorney General Robert A. Zarnoch.

His co-counsel, Assistant Attorney General Steven Sullivan, warned that the state has a compelling interest in preserving its law. To legalize same-sex marriage on a state level "would create a morass" of legal confusion among states and the nation, he said.

"It's an inescapable fact that federal law describes marriage as between a man and a woman," he added.

The U.S. Supreme Court has not taken a case on gay marriage, and states are hewing to their own ways for now. Only Massachusetts recognizes same-sex marriage. Several states and the District grant same-sex unions similar legal status to marriage. Other states, including Virginia, have passed laws banning same-sex marriage.

This year, the Maryland legislature passed a domestic partnership bill that would have granted some rights to gay partners who registered with the state. The measure was vetoed by Gov. Robert L. Ehrlich Jr. (R), who said it threatened "the sanctity of traditional marriage."

At Tuesday's hearing, Murdock listened and occasionally asked a question. She pondered the place of state courts in the national debate and wondered about the role of legislatures and the nature of marriage.

At one point, she turned to Choe. "There are thousands of years of tradition in which marriage has been defined," she said. "The court has to fly in the face of that tradition to find in favor of your clients."

Choe responded that if the tradition is rooted in discrimination, it is the duty of the court to recognize that and change it. He noted that Maryland was the first state to prohibit interracial marriage, a ban that remained in place until 1967.

Marriage confers a variety of rights, including spousal immigration benefits, hospital visitation privileges and the right to inherit property. Administrative assistant Takia Foskey and her two children have been unable to enroll in the insurance plan of partner Jo Rabb, a Baltimore bus driver. Marriage would allow them to. And marriage would allow Maria Barquero and Donna Myers, now separated by immigration law, to reunite.

Some of the rights might seem mundane -- but "if you don't have them," Polyak said before the hearing, "they are not mundane."

The benefits of marriage are most vital when a family is at its most vulnerable, plaintiffs said, such as when a child is born or when someone is incapacitated or dies.

When plaintiff John Lestitian, chief officer of code compliance for the city of Hagerstown, lost his partner of 13 years to suicide, he also lost the house they shared. He had to pay state taxes on half the balance of their joint bank account and financial penalties upon the retirement fund to which his partner had named him beneficiary.

Murdock said she would issue a written opinion on the case. Whatever the outcome, the case is expected to be appealed to the state's highest court.

Outside the courtroom, Rick Bowers, a Columbia pastor and chairman of Defend Maryland Marriage, said the Bible prohibits same-sex marriage.

He said the question belongs with elected officials, not the courts.

"I'm interested in seeing who is making the laws in our state -- our elected officials or appointed judges," he said.

That is exactly why these questions end up in court, Polyak countered. "Who would you have us rely on when one person can undo what the entire legislature did?"

In the meantime, living in legal limbo continues to have its challenges for Polyak and Deane.

"One thing that keeps us grounded is our kids," Polyak said. "They keep us in the present: getting uniforms ready for school, making sure everyone has a bath, that dinner is ready . . . making sure our family is intact, that everyone is healthy."

Gay couples and their supporters assemble outside the Baltimore courthouse, where the legal challenge was argued.Ann Nelligan brought her two children, Abby Ross, 2, and Jamie Ross, 5, from Takoma Park to support lesbian neighbor Risa Shaw, third from left.