There are some 250 prisons scattered across Brazil, with a similar number of police stations acting as improvised prisons. According to official figures, there are approximately 150,000 men and women in jail, out of a population of 175 million. (Scheffer and Marthe). Brazil's prison population grew 84% between 1995 and 2003, as governments eager to crush the crime wave in Brazilian cities encouraged the justice system to get suspects behind bars. Brazil's prison population grew 84% between 1995 and 2003, as governments eager to crush the crime wave in Brazilian cities encouraged the justice system to get suspects behind bars. Amnesty International estimates that a system with a capacity for 180,000 inmates is now holding at least 285,000.

In the late 90s the prevalence of HIV in Brazil's prisons was about 15% or one in seven prisoners – an astonishingly high prevalence in a country that had managed to keep its overall HIV prevalence low at 0.7% of the general population. This meant that one in 28 Brazilians with HIV was a prisoner.

Although there were no official statistics to prove it, AIDS, according to Ricardo Marins, an epidemiologist at the University of Campinas, was the leading cause of death in Brazilian prisons, killing more than violence or tuberculosis. For example, of 25 deaths registered at the prison hospital in Porto Alegre Prison in 1997, 21 were from AIDS. The same year researchers found that 17.3 percent of the detainees in Carandiru were HIV-positive while Sorocaba prison in Sao Paulo state, the rate was 12.5 per cent.

Cocaine is the drug most heavily implicated in the transmission of HIV. Cocaine is usually inhaled but in prison the small quantity of drug available makes injecting it into the veins more attractive to optimise its effects. According to another study of 115 HIV-positive prisoners carried out by virologist Jose Ricardo Pio Marins of the University of Campinas, 20 percent injected cocaine. According to the same research, about half of the prisoners had had a sexually transmitted disease in the last five years and most of them acknowledged that they had had sexual relations in prison. Sexual relations between prisoners are forbidden in Brazil and subject to severe punishment such as solitary confinement and a diet of bread and water.