Antiabortion activists opened a new frontier yesterday when they disrupted an ordination service at the Washington Cathedral because one of the five candidates is the wife of a doctor who runs an abortion clinic.

About 100 persons stood up when Bishop John T. Walker reached the part of the rite in which the Prayer Book directs him to ask the congregation " . . . if any of you know any impediment or crime because of which we should not proceed . . . . " The protesters shouted: "I object to the ordination of Susan Gresinger."

Gresinger's husband Thomas is a gynecologist who serves as medical director of the Northern Virginia Women's Medical Center.

Susan Gresinger, who declined to comment on the protest, was the only woman among the five ordinands, all of whom have just completed training at Virginia Theological Seminary in Alexandria.

Walker, who had met with leaders of the protest earlier in the week, yesterday permitted two protesters to approach the altar and then met with them in a side room while the congregation sang a hymn.

Returning, Walker told the congregation that the objections concerned abortion, which "the national Episcopal Church and this diocese have dealt with" in position statements that take a qualified prochoice stance.

"The person who has been questioned I believe to be in conformity with these documents, and we shall proceed," Walker continued.

Resuming the traditional ordination rite, he asked the congregation, "Is it your will that these persons be ordained?"

"It is!" the congregation roared back, as the demonstrators filed out to resume their protest in front of the cathedral.

In his sermon, Walker noted the rigorous preparation, supervised by church authorities, that priesthood candidates undergo. "It is clear that those who have come before you believe that they must challenge" the decisions of church leaders.

"There is no doubt that the act of abortion . . . is an ethical and moral issue" about which the church "has the right and duty" to speak, Walker said. "There are no easy answers to this terrible problem . . . . We should all of us pray that we be led to the truth . . . . "

He warned, however, that "we should not believe that we have the only answer."

The protesters, a Virginia-based group called Sanctity of Life, handed out leaflets charging that Thomas Gresinger is "one of the greatest perpetuators of abortion in the metropolitan community."

"Because their family lives abundantly off the profit of aborted babies, those objecting feel that Susan is an inappropriate candidate as a leader within the church."

Christy Anne Collins, a leader of the group, said the protesters were not deterred by the argument that the Episcopal Church, both nationally and locally, condones abortion. "We're working on changing that," she said.