BEIJING — An 80-year-old AIDS activist whom Chinese authorities have repeatedly blocked from going abroad left yesterday for America to receive an award from a group supported by Senator Clinton.

Gao Yaojie, a retired gynecologist, said she was still constrained by fears of reprisals when she returns home if she speaks too critically about China’s AIDS epidemic while visiting America.

“I feel confused, and I am in a dilemma,” Ms. Gao said at Beijing International Airport before boarding a flight to Newark, N.J. “If I don’t tell the truth, I lie to the people in the whole world. If I tell the truth, I am worried that I will be detained.”

She didn’t say specifically what issues she thought were taboo, but Ms. Gao embarrassed the government by exposing blood-selling schemes that infected thousands with HIV in the 1990s, mainly in her home province of Henan. Operators often used dirty needles, and people selling plasma — the liquid in blood — received replenishment from a pooled blood supply.

The Chinese government and the United Nations say China’s problem of tainted blood had largely been brought under control. Last year, only about 5% of new reported HIV infections were blamed on blood selling, which has been banned, or tainted transfusions, the Health Ministry says. But the legacy of the problem, which was initially covered up by the government, persists. Surviving victims say they have not been adequately compensated for their suffering and are unfairly discriminated against. Many children orphaned by the epidemic lack adequate care, Ms. Gao said.

In 2001, Ms. Gao was refused a passport to go to Washington to accept an award from a U.N. group, and in 2003, she was prevented from going to the Philippines to receive the Ramon Magsaysay Award for Public Service.

This month, she was kept under virtual house arrest for about 20 days as authorities tried to keep her from coming to Beijing to arrange a visa to America.

Ms. Gao said local authorities repeatedly warned her against going abroad, and for weeks, dozens of plainclothes police were stationed outside her apartment to prevent her from leaving. They relented, informing her on February 16 that she was free to travel.

She said international pressure, including separate appeals from Mrs. Clinton and human-rights groups, helped persuade authorities to let her go.

The decision marked a rare turnaround for Chinese authorities.