When he returned to China last March to visit his mother, Zhiyuan Wang brought back something he had acquired from his new home in America.

It landed him in jail almost immediately.

Wang, who has lived in Boston for five years and has practiced Falun Gong for much of that time, said he couldn't stand watching police persecute fellow members of the meditation movement for their beliefs.

With the indignation of an American who views freedom of association, speech, and religion as sacrosanct, the 48-year-old cardiologist marched into the local police headquarters in his hometown in Sichuan Province and demanded that police halt their campaign to stamp out Falun Gong, which leaders say has about 70 million members in China.

The police didn't flinch, he said. They arrested Wang and locked him in a small room. During his one-day detention, he said, they made him stand for hours and denied him food, water, and use of a bathroom.

''I thought the persecution was wrong, and I needed to do something about it,'' he said. ''I needed to tell the authorities the truth about what was happening.''

Yesterday, about 50 local Falun Gong members took to the streets in Boston to spread the word about the campaign, begun 17 months ago, to stamp out Falun Gong in China. According to their literature, tens of thousands of ''practitioners'' have been detained, beaten, forced from their jobs, homes, schools, and sent to labor camps. They say that at least 90 members have died in the past year in police custody.

Dressed in matching yellow sweatshirts bearing the Falun Gong motto, ''Truthfulness, Benevolence, Forbearance,'' the mainly Chinese immigrants spent about an hour stretching and meditating in front of the Christian Science Center before setting out on a long march through Boston.

Reaching to the sky to the direction of their spiritual leader, Li Hongzhi, [...]the peaceful group couldn't avoid an encounter with another authority.

A security guard from the Christian Science Center came out and told the group's leaders that they should not take pictures in front of the giant First Church of Christian Science.

''We are not here to bother anyone,'' said Michael Tseng, the rally's organizer. ''We're here only to raise awareness of the persecution and the atrocities.''

Among those atrocities, the Falun Gong says, was the death of Zhao Xin, a 32-year-old economics lecturer, in China. Police arrested her at Beijing Technical and Business University in June for openly performing her Falun Gong practices in a park. Three days later, according to the group, she was taken to a hospital with lacerations and bruises on her head and back and three vertebrae in her spine crushed. Members of the group said she died a few days ago.

For Wang and the others, the brutality is unconscionable. He was one of the lucky ones. Wang persuaded his guards to let him go, against the wishes of their superiors. If he hadn't, he said, he would probably still be in jail today.

''I am not afraid to say the truth,'' said Wang, now a medical researcher at Massachusetts General Hospital. ''But the truth needs to be heard by more people.''

http://www.boston.com/dailyglobe2/352/metro/