The five nurses and a Palestinian-born doctor were convicted of deliberately infecting Libyan children with HIV - charges they have always denied. A Libyan court earlier cleared nine policemen and a doctor of torturing the foreign workers into signing confessions.
Sofia-based journalist Virginia Savova looks at each of their cases for the BBC News website.
Ashraf Alhajouj was a trainee at the al-Fateh Paediatric Hospital in Benghazi when he was arrested on 29 January 1999 along with the five Bulgarian nurses who were also working in the city.
It took Mr Alhajouj's family 10 months of searching to find the exact jail where he was being held.
"We were startled when Ashraf came into the room, we simply could not recognise him," his father said in an interview for Bulgarian media.
"He had been tortured with electricity and different devices. He had been locked in cages."
Mr Alhajouj was born in the Egyptian city of Alexandria in 1969 and went to Libya when he was two years old.
His Egyptian mother Afifa was a computer literacy teacher and his Palestinian father Ahmed was a professor of mathematics.
Mr Alhajouj has said it is inconceivable he could harm Libyan children.
"I am innocent on all of the charges," he said at the final court hearing in 2006. "I was tortured like the rest of the accused and there are marks on the bodies of us all."
Mr Alhajouj's father insists his son is not yet a doctor but a student, as the Libyan authorities claim.
"If he really is a doctor, then Libya should show his diploma to the world," he said.
Mr Alhajouj's family also denies claims by the Libyan authorities that at the time of his arrest he lived in a luxurious property in Benghazi, and says he lived on a student campus.
After Mr Alhajouj's detention, his mother was sacked from her job and his sisters were expelled from university.
The family left Libya in December 2005 and went to the Netherlands, where they were granted political refugee status.
On 19 June, 2007 Bulgaria announced that it had granted citizenship to Mr Alhajouj, a decision that would enable him to leave Libya with the rest of the medics, if they are eventually freed.
Valia Cherveniashka, 52, is a nurse from the small north-west Bulgarian town of Biala Slatina.
She worked in a hospital in the Libyan city of Tarbouha from between 1984 and 1997 before moving to the al-Fateh Hospital.
She says she was beaten by Libyan guards but did not confess to infecting the children.
In 1999, Mrs Cherveniashka's husband, Emil Uzunov, was the first to bring the arrest of the medics to the public's attention in Bulgaria. In 2003, he staged a hunger strike at the Libyan embassy in Sofia.
husband of Valia Cherveniashka
Mr Uzunov and Mrs Cherveniashka's two daughters, Gergana and Antoaneta, have criticised Sofia's handling of the case, saying dozens of nationals from Poland, Thailand and other countries were also arrested but later released.
Mr Uzunov plans to initiate court proceedings against Bulgarian government officials, including the former foreign ministers of Bulgaria, Nadezhda Mihailova and Solomon Pasi, for failing to secure the release of the medics.
"If Bulgaria wants to wipe off the shame on its face, it should convict the inquisitors of the medics," he said.
Dr Anton Antonov, who was head of the paediatric ward of the hospital in Biala Slatina, where Mrs Cherveniashka first worked, told reporters that in a letter she wrote a month before her arrest, she wrote about the HIV/Aids outbreak in her ward and expressed fear for herself.
Dr Antonov described Ms Cherveniashka as a very good specialist and a lively person.
"It's absurd [to think of] her committing such an infernal act," added the doctor.
Snezhana Dimitrova, 54, worked as a nurse in two hospitals in the Bulgarian capital Sofia. She applied for jobs in Libya in the hope of earning a better salary, so that she could support her family.
She was arrested six months after her arrival at the al-Fateh hospital in 1998. She says it is inconceivable that a nurse and a mother could commit the crime of which she has been convicted.
Mrs Dimitrova claimed that during the initial stage of detention she was subjected to torture and inhuman treatment.
She has diabetes, had a nervous breakdown in 2005 and broke her leg last autumn.
Her husband George refuses to talk about his wife and family's ordeal.
Mrs Dimitrova has a daughter, a son and a seven-year-old granddaughter, whom she has only seen in pictures.
The health of her father, Ivan Klisurski, has suffered during the trial. After suffering a stroke 20 years ago, Mr Klisurski suffered another one after the announcement of the death sentence for his daughter in 2006.
He has only been able to speak with Mrs Dimitrova on the phone, and in an interview in 2007 he said he thought that he would not live long enough to see her again.
Nasya Nenova, 41, began her career as a nurse at the main hospital in the eastern Bulgarian city of Sliven, where she remained until she left the country to work in Libya.
She arrived in Libya in 1998 and started working at the al-Fateh. She was arrested just when she was preparing to return to Bulgaria.
During the investigation, she signed confessions, in which she stated that she had deliberately infected Libyan children in order to receive money.
At a court hearing in June 2001, Mrs Nenova and co-accused Kristina Vulcheva withdrew their testimony, explaining that they had been coerced by torture to confess to offences they had not committed.
husband of Nasya Nenova
Mrs Nenova told her husband Ivan later that she had been beaten with a cable on her hands and feet. As a result she said she could not walk for a week. A month later, she says she was subjected to electric shocks and threatened to be infected with HIV if she did not confess.
After three months in jail, she tried to commit suicide. Asked by a judge whether her suicide attempt was a result of a guilty conscience, she replied that she had tried to end her life because she could not bear to be tortured.
Ivan Nenov, an anaesthetist in the Intensive Care Unit of the Sliven's hospital, has strongly criticised the Bulgarian authorities for not succeeding in freeing the medics. He and Antoaneta Uzunova, the daughter of Valya Cherveniashka, were the first relatives to visit the medics in 2001.
From Libya they issued a joint declaration in which they accused the Bulgarian authorities of hiding the information about the tortures on their relatives for more than a year.
"Now the authorities are concerned about our relatives, but it is hopelessly late," Ms Uzunova and Mr Nenov said at the time.
"Libya will trade the Bulgarian medics at the price it wants," Mr Nenov said in 2005.
Mrs Nenova has had the unanimous support of her colleagues at the city hospital in Sliven throughout the past eight years.
They have held rallies calling for her and her colleagues' freedom.
Mrs Nenova has a son who was in secondary school when she was arrested and is now at a university in France.
Valentina Siropoulo, 48, was a nurse for 18 years in the Intensive Care Unit of the hospital of the Bulgarian city of Pazardjik. She went to Libya so that she could earn more money to send her only child to university.
Mrs Siropoulo had been working at the al-Fateh since February 1998.
She says she is innocent and that she showed compassion to the children in the Aids ward where she worked.
"They... have done to me so many things but they can't take my innocence from me," she said in court in 2006.
She said beatings and torture with electric shocks during the investigation left her with partial paralysis to her face and unable to talk for months.
In her first card to her family after 22 months of detention, she wrote:
"Hello, dear family. I am allowed to write you a letter, which doesn't mean it will reach you or that there'll be another one. Physically I am relatively fine, but my soul is incurably ill.
"The belief in good and truth, in the fact that you exist, that there is someone thinking about me, that I want very much to see you, gives me strength to fight the evil and to continue to live."
Ms Siropoulo's former colleagues from the hospital in Pazardjik have held rallies and silent vigils.
Kristina Valcheva, 48, arrived in Libya from Bulgaria with her second husband, Dr Zdravko Georgiev, in 1991.
She was working in the Hauari Hospital in Benghazi when she was arrested over the outbreak of HIV/Aids among children in the Paediatric Hospital.
Libyan prosecutors say she is the mastermind behind the case, basing their evidence on HIV-infected blood bags found in her house in Libya, although she never worked in the Paediatric Hospital itself.
Mrs Valcheva has said that during the investigation she was subjected at least 10 times to electric shocks. She was undressed and beaten with an electric cable.
mother of Kristina Valcheva
In February 1999, her husband was also arrested when he went to look for his wife in the police office. Dr Georgiev was detained and accused with the five other Bulgarians although he did not work in the same Paediatric Hospital.
On the day his wife was sentenced to death in 2004, Dr Zdravko Georgiev was released from jail, but he is still not allowed to leave Libya. He is staying at the Bulgarian Embassy in Tripoli.
Mrs Valcheva has a 29-year-old son from her first marriage.
Zorka Nachkova, Mrs Valcheva's mother, says she dreams of the day she returns home.
"'I'll hold her and won't let her leave my arms for a whole night," she said.