The gel uses an AIDS drug along with a zinc compound and protected all animals tested from infection with the monkey version of HIV, the researchers report in the Public Library of Science open-source journal PLoS ONE.
It "afforded full protection (21 of 21 animals) for up to 24 hours after two weeks of daily application," they wrote.
The gel uses a very small amount of active drug and thus might be safe and cheap, said the Population Council in New York, which led the study.
The study joins a growing body of experiments that are beginning to show progress in preventing AIDS, a fatal and incurable virus that infects 33 million people globally and which has killed 25 million.
Melissa Robbiani of the Population Council, who worked with the National Cancer Institute and other laboratories to test the gel, is hoping to test it on people.
In July researchers stunned AIDS experts when they found a similar gel using the Gilead Sciences AIDS drug tenofovir reduced HIV infections in women by 39 percent over two and a half years.
Non-profit groups are moving ahead to develop that gel and the U.S. Food and Drug Administration has given it fast-track designation.