The sister of Judith L. DeMaria, the woman who went jogging around lunchtime a week ago today and didn't come back, is all right until she starts thinking and getting quiet, according to her husband. Then she starts to cry.

"The waiting is the worst part about it," DeMaria's brother-in-law, Dan Weaver, 37, said yesterday. "There are so many unknowns . . . it makes us insecure."

DeMaria, 27, a tennis pro and sales representative at the Capitol Courts Club in Sterling, had left the club about 11:30 a.m. to jog. She was last seen by a park ranger as she approached a wooden bridge along the Washington and Old Dominion bike path. Loudoun County sheriff's deputies, officers from other law enforcement agencies and as many as 100 volunteers at a time have been searching night and day for clues.

A "substantial amount" of human blood was found last Saturday by a trained dog near Broad Run Bridge, but the sheriff's department -- and the family -- are still awaiting a report on the blood type from a state forensic lab in Merrifield.

Family members, who have been unable to locate DeMaria's birth certificate, are trying desperately to learn her blood type.

"We've been checking with doctors we knew she had visited," Weaver said. "If you tried to go back and research your blood type, you'd have a hard time."

Weaver, whose wife declined to be interviewed, said DeMaria had had a minor operation in New York and relatives tried there, but "we drew a blank."

Then they remembered that DeMaria was required to get a physical for a job at a West Virginia resort. But it turned out that a blood test had not been required.

Now the family plans to try California, where DeMaria was hospitalized as an infant.

"That's the next thing we're going to pursue," said Martha Whitestone, 44, DeMaria's stepmother. "As an infant, she was quite ill and was hospitalized."

"The only reason I know my blood type is because I donated blood," Whitestone said. "It's important for people to know."

Whitestone, who works for United Airlines in the McLean reservations office, said that all the family can do is wait. Both she and her husband, John, an automation specialist for United Airlines at National Airport, have left work to sit by the phone in their Fairfax home.

"The difficult thing we have to deal with is not knowing," she said. "Tragedies you can deal with."

She said family members and friends, who said DeMaria -- known as Judi -- got along with everyone, are drawing comfort from the support they have received.

"It's important for people to know that there are so many good people out there," said Whitestone, who said she is afraid that she will not be able to thank everyone. "Even when someone bad is out there, there are thousands and thousands who are good."

Deputy Sheriff Robert E. Turner, one of two investigators in charge of the DeMaria case, said that he has received innumerable telephone calls and tips.

"We're getting calls from Vienna to Purcellville," said Turner, who keeps the family and the FBI informed daily. He said that some of the callers may have seen DeMaria -- described as 5 feet 6 inches, 140 pounds, with black hair and brown eyes -- on the path before she disappeared.

Turner said authorities are sorting through the tips and investigating the background of DeMaria, who lives alone in Manassas and works at the club at 308 Glenn Dr., 1 1/2 miles from the bike path.

Meanwhile John DeMaria, Judi's father, sits at home and waits.

"I've got a good wife, and good people helping," he said.