Activist, in jail
Hu Jia, probably China's most prominent activist, was sent to prison for three-and-a-half years in April 2008 for writing five articles and giving two interviews.
He has long sought to publicise what he believes are injustices in China concerning the environment, HIV/Aids and human rights.
In April, Beijing's First Intermediate People's Court interpreted these acts as an attempt to subvert "the state's political and socialist systems".
But human rights groups say the Chinese authorities put the campaigner in prison to silence him ahead of the Olympic Games.
As well as being sent to prison, Mr Hu was deprived of political rights for one year.
The state-owned Xinhua news agency reported that Mr Hu wrote articles criticising the Chinese political system, and accepted interviews with foreign journalists.
"Hu spread malicious rumours, libel and instigation in an attempt to subvert the state's political and socialist systems," it said.
Mr Hu suffers from liver disease due to Hepatitis B infection. Amnesty International says the family has been unable to provide him with medicine. He is receiving some medication from prison authorities, but his family are concerned that this may not be adequate.
Human rights groups say they are also concerned about Mr Hu's wife, Zeng Jinyan, herself an activist. She has been held under effective house arrest, with her young child, since Mr Hu's detention.
Writer and lawyer, presumed in jail
Gao Zhisheng is a writer and self-taught lawyer who has become famous for defending Chinese citizens against the state.
His pro-bono work has included cases for evicted homeowners, human rights activists, underground Christians and members of the banned Falun Gong spiritual movement.
He has published a book called "A China More Just" detailing his experiences of confronting China's legal and political system.
In August 2006, Mr Gao was arrested and held in Beijing charged with inciting subversion of state power through his writing.
He was sentenced to three years in prison in December 2006 but the jail term was suspended for five years. He was also deprived of his political rights for one year.
While he was held in custody the authorities used force and threats against his family in an attempt to coerce Mr Gao into informing on other activists, says US-based Human Rights Watch.
Mr Gao has also been beaten and harassed while not in prison and was reportedly the target of an assassination attempt.
He has not been seen since he was taken from his home in September 2007 - although it has been alleged that he has attempted suicide.
Activist, in jail
Ye Guozhu was sentenced to four years in jail in 2004 after he tried to organise a demonstration against evictions in Beijing.
He was arrested after he applied to stage a 10,000-strong rally in the Chinese capital and was found guilty of disturbing the social order and convicted for "picking quarrels and stirring up trouble".
He had been protesting since his family's home was knocked down in 2003 to make way for a wave of planned redevelopments ahead of the Olympic Games.
He was due to be released on 26 July at the end of his sentence, but Amnesty International has said it is uncertain whether he will be freed.
The group says authorities may use his attempts to challenge his conviction as a pretext to extend his imprisonment beyond the Olympic Games.
He reportedly continues to suffer from health problems, partly as a result of being beaten with electro-shock batons and being subjected to periods of "discipline" in prison, says Amnesty.
Activist, in custody
Ni Yulan, an activist who has campaigned for the rights of people evicted from their homes, will go on trial on 4 August, four days before the start of the Olympics.
The former rights lawyer, who was disbarred in 2002, will be tried for "obstructing official business".
The crime carries a maximum punishment of three years in jail.
Ms Ni has spent almost a decade assisting victims of forced eviction in the Chinese capital, many of whom lost their homes to make way for Olympic facilities.
She previously spent a year in jail, and she is unable to walk without the aid of crutches due to past police mistreatment, according to Chinese Human Rights Defenders, a network of rights advocates.
Her husband, Dong Jiqin, believes her current detention was mainly to ensure that she would not make trouble in the period before the Olympics.
Lawyer for abused women, in jail
Mr Chen, a blind activist known as the "barefoot lawyer", clashed with the authorities over the enforcement of China's one-child policy.
He defended women whom he said were being forced into late-term abortions and being sterilised by over-zealous health officials in Linyi city, Shandong Province.
He was sentenced to four years and three months in prison in August last year, after being convicted of damaging property and disrupting traffic.
The sentence drew international criticism, with campaigners and supporters claiming that the prosecution was politically motivated.
Mr Chen, who remains in jail, has won several international awards for his work.
GEDHUN CHOEKYI NYIMA
Tibetan religious leader, uncertain whereabouts
In 1995, six-year-old Gedhun Choekyi Nyima was selected by the Dalai Lama as a spiritual leader of Tibetan Buddhism.
He was seen as the reincarnation of the Panchen Lama - the second-most important figure in Tibetan religion, culture and politics after the Dalai Lama himself.
Three days later he was detained by the authorities - the last time his supporters saw him.
Mystery surrounds his fate, although officials in Tibet told the BBC last year that he was living a quiet life in the capital, Lhasa.
Beijing installed their own boy, Gyaincain Norbu, as the 11th reincarnation of the Panchen Lama - although most Tibetans are thought to remain faithful to the Dalai Lama's choice.
Former mandarin, under house arrest
Bao Tong was an adviser to the Communist Party's general secretary Zhao Ziyang at the time of the Tiananmen Square massacre in 1989.
Both men had opposed the brutal crackdown on the protesting students, and both suffered for their stance.
Mr Zhao was replaced as party boss by Jiang Zemin, and Mr Bao was handed a seven-year jail term.
Since his release, he has lived under house arrest, managing to smuggle out occasional essays criticising China's one-party rule.
In a letter released at the time of his former boss's death in 2005, Mr Bao wrote that the authorities were "constantly worried about Mr Zhao and determined to erase his name from the hearts and minds of the people".
His letter went on: "Their purpose is none other than to prevent 1.4 billion people from advancing toward a society of modernity, democracy and law."
Journalist, in jail
Shi Tao, who worked for the Contemporary Business News in China, was jailed for 10 years in 2005 for "divulging state secrets".
It is thought he sent an e-mail describing the efforts made by the Communist Party to censor reporting in the run-up to the 15th anniversary of the Tiananmen Square massacre.
His case has become a cause celebre for free speech campaigners - not least because internet firm Yahoo has been accused of informing on him.
The US-based web giant was said to have passed on details of his whereabouts to the authorities.
Mr Shi - a writer and a poet - was awarded the Golden Pen of Freedom from the World Association of Newspapers earlier this year.
HIV/Aids activist, lives in Henan province
Dr Gao is famous for exposing China's worst HIV scandal.
Her work helped to reveal how corrupt blood-selling deals infected thousands of people with the virus in the 1990s.
Companies known as "bloodheads" offered money to peasants in return for donations.
The firms - run by officials and businessmen - would take the blood, remove the plasma and inject the remaining blood back into the peasants - often using dirty needles or infected blood pools.
Dr Gao overcame a climate of secrecy to end the practice and draw attention to the scandal.
The authorities were initially lenient with her, but Beijing grew uncomfortable with her criticism of provincial Communist leaders.
She has been stopped from going abroad twice since 2001 to receive prizes, and is said to have undergone several periods of house arrest.
Earlier this year, she was allowed to visit the US to collect a prize from Vital Voices, a non-profit group supported by Senator Hillary Clinton.