Members of an animal rights organization based in Delaware yesterday joined efforts on behalf of 15 research monkeys at the National Institutes of Health by staging a noontime vigil at the Bethesda facility. The vigil, attended by more than 50 persons, marked the 49th day of a hunger strike by animal rights activists to draw attention to the conflict over the use of the monkeys for research.

Lorri Bauston of the Wilmington, Del.-based Farm Sanctuary organization said that 49 persons from around the country fasted yesterday to demonstrate support for the hunger strike begun by sanctuary vice president Stas Kaczorowski April 28.

Members of a group called People for the Ethical Treatment of Animals have been protesting outside NIH since April in an effort to persuade officials to transfer the animals to a primate sanctuary in Texas.

NIH officials said Friday that they are searching for place to send the monkeys. They said the animals will undergo no further "invasive procedures for research."

Bauston said yesterday that Kaczorowski is in a weakened state and will continue to consume only about a cup of juice a day until the monkeys are freed.

"He is prepared to die," she said.

Doyle Stanley, a Navy man whose career nearly ended in February 1985 following sinus surgery by military doctors two years before, is still ill. But he says he now has confidence in the care and treatment he is receiving as the result of a promise by Navy Secretary John Lehman.

The January 1983 operation to remove a benign sinus tumor led to a virulent staph infection that the petty officer from Virginia Beach, Va., claimed went unchecked for months. That infection caused his skull to deteriorate, threatened his life and pushed him to request civilian care.

Stanley, 30, the father of two, has spent the past six months under hospital care fighting other bacterial infections in the sinus area, and last month was transferred to Atlanta for civilian treatment.

Stanley's ordeal, chronicled by The Washington Post in early 1985 as a case of questionable military health care, came to the attention of Lehman. He promised that Stanley, then a 12-year veteran, would receive the "best medical care the Navy can muster," even if it meant receiving civilian care.

Since then, Stanley has had civilian doctors monitor his illness and has undergone two more operations to try to stop the infection. He appeared to be recovering and began working full time at Oceana Naval Air Station in May 1985.

Infection reappeared last December, and Stanley was hospitalized until two weeks ago, when he was discharged to outpatient care.

"The last few months haven't been so good, but now I'm feeling a little bit stronger every day," Stanley said. "But it's slow . . . . I haven't had any complaints at all with the Navy , either with them paying the bills or getting the doctors I requested."

His wife, Sandy, said, "At one point, he was doing so badly, we weren't sure he could make it." She added that the Navy fulfilled and continues to fulfill its promise to pay for care and to allow her husband to remain in the Navy.

Dr. John Drummond, the Atlanta physician who now is treating Stanley, said Friday that Stanley is receiving daily antibiotics and will receive treatment for at least two more months.

"One of the major problems is, in the past, he's received treatment for a week or two, felt better and then redeveloped an infection," Drummond said. "My game plan is to do it long enough . . . so that the infection won't return."

Stanley lost nearly half his skull to the disease and must wear a protective helmet. He experiences headaches and dizziness and must be cautious about any activity that could result in injuries.

He hopes someday to have an artificial forehead implanted, but for that he must remain infection-free for a year, according to doctors.