SAN FRANCISCO (AP) _ One in four medical interns surveyed at the University of California at San Francisco said they were stuck with needles contaminated by the AIDS virus in a 12-month period, said a study released Wednesday.

About 25 percent of interns who responded to the survey said they were stuck by HIV-infected needles during the period ending in January 1989, said the study published in this month's American Journal of Medicine.

The study was handed out to reporters at a news conference called by a union representing San Francisco physicians, medical students, nurses and other health-care workers.

About 55 percent of surveyed residents and interns in internal medicine at the university's three hospitals accidentally stuck themselves with needles containing blood of patients known to be HIV positive or at high risk of being so, the study said.

The San Francisco Interns and Residents Association, which sponsored the study, urged administrators to change what it called atrocious working conditions at the three hospitals.

The study was conducted by Dr. Carol Mangione, a former chief resident at the university who is now at Beth Israel Hospital in Boston. She sent the survey to about 120 interns and residents and received replies from 86.

''It's an area that's being brushed off by administrators,'' said Dr. Carole Macaulay, president of the California Association of Interns and Residents, or CAIR.

CAIR is the parent organization of the San Francisco union.

''Over the years we've voiced concern and been met by minimal and sometimes no response,'' Macaulay said.

At the news conference, CAIR members blamed working conditions for the high AIDS risk to student doctors. Exhausted physicians, who routinely work 100 hours a week - including 36-hour shifts without a break - are often forced to do routine blood draws, the union said.

The union estimates the risk of on-the-job HIV exposure to medical interns at the three hospitals at four times the annual fatality rate of California police officers and 10 times that of the state's firefighters.

However, several studies on the risk of AIDS infection from needle sticks show that the actual risk of contracting AIDS from an HIV-exposed needle is between 1 in 200 and 1 in 500, said Mark Madsen, director of the California Medical Association's Department of Physical Education.

''Generally, in the needle, there's so little (of the virus) there that you won't get enough in your system to multiply and cause an infection,'' said Steve Heilig, an associate at the San Francisco Medical Society, which represents 1,800 of the city's physicians.

Heilig said the danger of being stuck or exposed to the virus has been reduced since 1988 with better risk training for doctors.

Doctors ''need to wear gloves and gowns and masks and shields when there is a possibility of exposure. That's not always being done,'' Madsen said.

At the news conference, doctors displayed syringes, needles and other devices with safety attachments that reduce the risk of sticks and said the university won't spend the money to buy the equipment.

The union is asking administrators of the hospitals to provide 24-hour blood-drawing teams and university-paid disability insurance coverage. The union is also lobbying state legislators for laws to reduce working hours for residents and interns.

James Tusky, a chief resident at one of the hospitals, said he spent years denying the risk of HIV infection to doctors. Then, in his third year of residency, he stuck himself with a needle that had just come out of an AIDS- infected man.

''My world changed. The feeling you get looking down and seeing blood oozing out of your finger is one that I hope no one here will ever have,'' Tusky said. ''It changed my life. It changed my sex life.''

He remains HIV negative six months later.