Veteran state Sen. Clive L. DuVal II (D-Fairfax) beat back a determined attempt by Republicans to unseat him last night, but Sen. John W. Russell (R-Fairfax) lost to the person he defeated four years ago, Democratic activist Emilie Miller.

In other contested Northern Virginia General Assembly races, Del. Leslie Byrne (D-Fairfax) defeated Republican lawyer A. Strode Brent and the GOP held onto a seat being vacated by Del. Stephen Gordy. In that race, Republican teacher Jane Woods beat Democratic lawyer Jeffrey Fairfield.

But while Northern Virginia's legislative delegation appeared to remain relatively stable, some well-known incumbents in both parties were defeated around the state. In the Richmond suburbs of Henrico County, Democratic state Sen. William Parkerson was trailing Republican activist Edwinna P. (Eddy) Dalton, the widow of former Gov. John N. Dalton.

State Sen. A. Joe Canada Jr. (R-Virginia Beach) was defeated by Moody E. (Sonny) Stallings, a Democratic lawyer. Canada had been linked in recent years to two Tidewater businessmen whose dealings have been investigated by federal authorities.

DuVal, who has been in the Senate since 1972, faced a serious challenge from Republican Bobbie G. Kilberg, a lawyer who had served in the administration of President Gerald Ford. Kilberg counted on strong Republican support from voters in the 32nd District, which includes McLean, because they tend to vote Republican in national elections. She also had been able to raise a healthy campaign treasury, and was boosted by an appearance by Vice President George Bush.

But DuVal had made few enemies in either party. He stressed his position as a senior member of the Senate's Democratic majority, an advantage that gives him leverage in state financial matters. With all of the district's 43 precincts reporting, DuVal had 54 percent of the vote to Kilberg's 46 percent.

In central Fairfax County's 34th District, Russell and Miller staged a rematch of their 1983 election, which Russell won by 350 votes. This year, the outcome changed, but the margin was equally narrow. With all 43 precincts reporting, Miller beat Russell by about 600 votes.

Miller charged in her campaign that Russell had failed to make any impact in the legislature, introducing only eight bills and rating low in an "effectiveness survey" conducted by a Norfolk newspaper. But Russell, a former mayor of Fairfax City, said he had been a quiet lawmaker who had concentrated on representing his district rather than generating headlines.

In contrast to most campaigns, Miller was able to raise more money than her incumbent opponent. And she also had help from some of the state Democratic Party's leading lights -- the governor, lieutenant governor and attorney general made appearances for her.

Byrne, a first-term delegate who represents the 38th House District, was considered vulnerable because her district is almost evenly divided among Democrats and Republicans. And Brent, her GOP adversary, had compiled a long record of community service.

But Byrne, too, emphasized her ties to the General Assembly's Democratic majority party, and voters seemed to agree that the party influence is valuable. With all 19 precincts reporting, Byrne had 52 percent of the vote to Brent's 48 percent.

In central Fairfax's 37th District, Woods took what was expected to be a close race with Fairfield and turned it into a rout. Fairfield had narrowly lost two years ago to retiring Del. Gordy. But with all 14 precincts reporting, Woods won by a margin of 58 percent to 42 percent.

Among the remaining Northern Virginia lawmakers, all were either unopposed or were easily reelected. A number of senior legislators, including House Appropriations Committee Chairman Dorothy S. McDiarmid, D-Fairfax, and Senate Privileges and Elections Committee Chairman Joseph V. Gartlan Jr. (D-Fairfax) breezed to new terms.

Yesterday's election made virtually no difference in the partisan balance of power within the General Assembly, which is overwhelmingly Democratic. Before the voting, Democrats controlled 31 of 40 Senate seats and 65 of 100 House seats. Late last night, a spokesman for the Republican Party of Virginia, Steven Haner, said that the GOP would gain no more than one or two seats in each House and could lose a Senate seat.

Before voting began, Republicans had predicted just before the election that they would pick up three seats in each chamber. Haner said the GOP's disappointing showing was owed largely to the unexpected defeat of several incumbents around the state.

"We didn't do as well as we had hoped, but we feel fine to have held our own in the face of a fairly strong Democratic effort," Haner said. "We missed some opportunities. But we concentrated a lot of our resources on the Parkerson-Dalton Senate race {in Henrico County}, and that may have distracted us."

Julia Sutherland, a spokesman for the Virginia Democratic Party said, "With a couple of races still too close to call, our worse case scenario is a loss of one seat in the House and Senate. We see this as a shining victory.

"Back in March the Republicans were saying they were going to get five seats in the Senate. They didn't come close. We are pleased and delighted."

But the Republicans found some solace in unseating Henrico County's Parkerson, the most senior member of the Senate. Dalton and Parkerson waged by far the most expensive state legislative race ever, spending more than $1 million between them. The previous spending record for General Assembly campaign was about $250,000.

Two incumbents in the Tidewater area were unseated. Democrats knocked off Virginia Beach's Canada, capitalizing on his financial troubles. And in Chesapeake, Democrat William T. Parker, a member of the assembly since 1976, was felled by Republican lawyer Mark Early, a first-time candidate.