Cuba's secret police threw them in jail and called them "salaried puppets" of U.S. aggression. Yet the dissidents persevered, defiant voices of discord in a regime that demanded near-absolute loyalty.
"Our duty is to think independently of the monopoly on thought held by the Communist Party. Our mission is to simply stand up and say, 'I think differently' " said Ricardo Bofill, founder of the Cuban Committee for Human Rights.
For decades, thousands of Cubans languished behind bars for speaking out against Fidel Castro, his revolution or his communist government.
Many served long and harsh terms in dingy prisons, thrown in with common prisoners on ill-defined charges of "enemy propaganda" or "dangerousness." Amnesty International in 2003 declared 90 of them as "prisoners of conscience," making Cuba the country with the highest number of prisoners with that status in the Western Hemisphere, even as Cuban dissidents claimed the real number of all political prisoners was well over 300.
But many more stayed on the streets, gathering 11,020 signatures in 2002 and another 14,384 the following year for the Varela Project, a daring proposal to hold a nationwide referendum on the communist system.
A broad array of other "independent" groups, including teachers, librarians, artists, ecologists, journalists, economists and lawyers, also disputed the government version of Cuba's reality but rejected the term dissidents.
Havana officials called them all traitors seeking U.S. dollars or visas as "victims" of political persecution - nothing but a handful of malcontents unknown to most Cubans and mocked by their isolation.
But they persevered: the Varela Project's unassuming mastermind Oswaldo Payá; the feisty Oscar Elías Biscet; economist Martha Beatriz Roque; journalist Raúl Rivero; activist Gustavo Arcos, who died in August 2006; former MiG pilot Vladimiro Roca; and Elizardo SÍnchez, a former university professor of Marxism.
The repression began in the early years of the revolution when men, women and children accused of counter-revolutionary acts were thrown into prison. Sentences were long and living conditions harsh. Some who came to be known as plantados - the steadfast ones - refused to be treated as common criminals and remained naked rather than wear prison garb.
"They tried by every means to dehumanize people," said José Pujals Mederos, a plantado who served 27 years and 22 days in jail. Prison officials retaliated against the plantados by denying them family visits, sometimes for years.
The plantados were also subjected to frequent beatings. Medical care and nourishment was scant. And the forced isolation from loved ones brought with it an overwhelming sense of loneliness.
"We would go for months without clothing," said Jorge Valls, a plantado who spent 20 years and 40 days in prison. "We were naked cave men in a 20th century cave."
Beyond the dehumanizing conditions, these political prisoners also lived with the constant threat of death. Valls remembers hearing executions being carried out nearly every night while he was held at the La Cabaúa prison in Havana.
British historian Hugh Thomas wrote in his 1971 tome on Cuba that "the total number of executions by the revolution probably reached 2,000 by early 1961, perhaps 5,000 by 1970 - But who can be certain of figures in this realm?"
La Cabaúa was infamous as one of the worst prisons on the island. The cell blocks were 60 feet long and 25 feet wide. Iron beds were stacked four high, with just 16 inches between each bunk. The rows of iron were separated by a central walkway about six feet wide.
Each cell block accommodated a total of 304 men. They shared two toilets and a small cubicle that enclosed a primitive shower and wash basin. At night, those without bunks had to sleep wherever they found space - up against the wall, on the floor under the beds or along the walkway.
Their diet consisted mainly of macaroni, boiled peas, canned food, eggs or stale bread. The food often was laced with worms, cockroaches or weevils. Water was usually available only twice a day, and always cold.
Women accused of political crimes were sent to prisons in Guanajay, Matanzas, Guanabacoa and Santiago de Cuba. Some also served their sentences at prison farms and forced-labor centers. Pinar del Río housed the prison for minors, some as young as 11.
The harsh treatment persisted through 1978, when Cuba reached an agreement with the United States on a massive release of prisoners. Castro agreed to free most of the 4,500 political prisoners held at the time, including some 500 plantados.
While repression was always present, during the 1980s there seemed to be some level of government tolerance for dissent. Elizardo Sánchez founded the Cuban Human Rights Committee at the time, and Gustavo Arcos would follow him as its secretary general in 1988.
But by the late 1980s, the government was cracking down on dissent again. Hundreds of activists were arrested in a series of sweeps that lasted through the early 1990s, and Cuban jails again were jammed with political prisoners.
With the collapse of the Soviet Union in 1991, the Cuban opposition began getting the kind of recognition the West had once bestowed on Eastern European dissidents, receiving awards and cash from international groups.
The international attention prompted Castro's government to change its repressive tactics by switching long prison terms to shorter jail sentences, harassment detentions and pressures to leave the country. Yet the opposition movement continued to grow, spreading from Havana to the provinces and moving beyond human rights to issues like the environment and religion.
The number of dissidents was estimated in the late 1990s at 3,000, far more than were active in the Soviet Union in the 1980s.
Yet they remained mostly unknown, seldom mentioned in the Cuban media unless it was to denounce them.
Another harsh crackdown occurred in 2003 with the arrest of 75 dissidents and their sentencing to up to 28 years in prison after summary one- and two-day trials.
In a handful of letters smuggled out of jail, the dissidents described living conditions reminiscent of those experienced by the plantados - tight, filthy quarters infested with rodents and bugs; food too disgusting to eat; limited access to medical care; and physical and mental abuse.
Some of those prisoners have been released, including four dissidents who were sent to Spain recently, a move that human-rights activists condemned as "forced exile."
Their release cuts the number still held to 55.
In the 18 months since ailing Cuban leader Fidel Castro turned power over to his brother Raúl, the number of dissidents held for political crimes such as "dangerousness" or rebellion has dropped by 82. Cuba still holds an estimated 230 political prisoners, according to human-rights activists.
Vladimiro Roca, a government opponent and son of a former Communist Party leader, who served nearly five years in a maximum security prison, said prison descriptions in letters smuggled out of jail do not fully capture the horror.
"It's hard to put into words what prison conditions are like here," Roca said from Havana. "You have to live it to believe it. In reality, most of the inmates that were in that prison with me should have been dead. That's how bad it was."