PHOENIX (AP) _ Information about AIDS has steadily grown among adult Americans, but there has been a significant increase in those who falsely think people who donate blood risk getting AIDS, researchers reported Saturday.

''It's a real piece of misinformation ... the one belief that seems to be intransigent, and we don't know why,'' said Eleanor Singer, a sociologist at Columbia University.

Ms. Singer, Theresa F. Rogers and Cydnee Blattner collected more than 70 non-governmental surveys including 650 AIDS-related questions measuring public knowledge, attitudes and behavior.

They examined trends in public fear and disapproval as well as compassion and tolerance regarding the disease. The findings were reported at the annual convention of the American Association of Public Opinion Researchers, meeting in Phoenix through Sunday.

Polls show the percentage of people who thought AIDS could be transmitted without sexual or blood contact has decreased from a high of around 50 percent in the mid-'80s - for a question about kissing - to a high of 24 percent in 1990, the report said.

But the percentage who held the mistaken belief that AIDS could be caught by donating blood increased from 29 percent in 1988 to 44 percent in 1989, the report said.

The report contained a renewed plea to the nation's pollsters to regularly ask some standard questions about AIDS. Ms. Singer and Ms. Rogers, both senior research scholars at Columbia, have been studying trends on AIDS for several years and say it is becoming increasingly difficult to sort out true change in attitudes from variations in polling methods.

The report traced trends since 1986, when public information about AIDS was enhanced by the release of a surgeon general's report. The next year, media coverage surged, and in 1988, the government mailed a pamphlet about AIDS to every household.

''But since 1987, both media coverage and government attention have declined,'' Ms. Rogers said. ''It is too early to tell what the consequences of this decline are likely to be for public information, attitudes and behavior, especially because polling (about AIDS), too, seems to be on the decline.''

In a related Gallup Poll published Sunday in The New York Times, an overwhelming majority of those questioned favored testing doctors, dentists, nurses and hospital patients for AIDS.

Forty-six percent said all Americans should be tested, down from 52 percent who held that view in a June 1987 Gallup survey. Fifty-nine percent said people with the virus be required to keep a card identifying them as AIDS carriers.

The Gallup Poll sampled 1,014 randomly selected adults nationwide from May 2-5. It had a sampling error of plus or minus four percentage points.

Jane Stokes of the University of Southern California reported on another study in which interviewers let people explain AIDS in their own words. This approach confirmed the increase in understanding of the virus, but turned up underlying harsh attitudes the polls miss, she said.

''The high knowledge of the facts of HIV transmission doesn't protect them from prejudice against people infected with HIV,'' she said.

Polls have found only around two-thirds of the public willing to work alongside someone with AIDS and about half willing to send their own child to a school where another child has AIDS.

The perception that AIDS is likely to spread to the population at large remains at around 70 percent, the Columbia researchers said. But concern about AIDS as a personal health threat has not increased since the mid-'80s, the report said. About one-fifth say they are ''very concerned'' and another fifth are ''fairly concerned.''

The polls have not been encouraging for those marching in the streets to promote AIDS awareness. When Americans are asked to name the country's most important problem, without the prompting of a list, 1 percent to 3 percent mention AIDS. No more than half mention AIDS as the most urgent health problem facing the nation, although its mentions are greater than those for any other disease.

As of the end of March, the federal Centers for Disease Control had recorded a cumulative total of 171,876 cases of AIDS in the United States, with 108,731 deaths, or 63 percent of all cases. The Public Health Service estimates about 1 million Americans are infected with HIV, the AIDS virus.

Polls have not shed much light on what percentage of the public is willing to be tested for HIV. The results vary widely with different question wording.

''But there is some indication of increased insistence on involuntary testing of 'high-risk' groups, from 49 percent in 1987 to 57 percent in 1989, as well as increased support for tracing the sexual partners of people who have tested positive to AIDS antibodies,'' the report said.