By Damian Grammaticas
BBC Moscow correspondent
Some two thirds of prisoners in Russian jails are ill, a senior official in the justice ministry has said.
The government is trying to tackle overcrowding
The chief of the penal directorate, Vladimir Yalunin, said about 500,000 prisoners suffered from a range of complaints from mental illness to Aids.
Russia jails a greater proportion of its people than any other major country in the world, apart from the US.
Russian prisons are often overcrowded places that are breeding grounds for disease.
Three quarters of a million people are currently in Russia's jails or remand centres. According to Mr Yalunin, speaking in an interview with Interfax news agency, two out of every three are ill.
About 120,000 have psychiatric disorders, almost 90,000 are drug addicts, more than 50,000 have tuberculosis, and 35,000 are HIV positive. Chronic alcoholism is also rife.
The government is trying to tackle overcrowding by introducing alternative sentences.
And a multi-million dollar programme supported by the World Bank has helped reduce tuberculosis rates by funding the purchase of medicines and X-ray equipment.
Mr Yalunin said Russia was also planning to apply to the Global Fund to Fight Tuberculosis, Malaria and Aids for further help.
But a jail sentence in Russia means time inside a grim institution, and also the real possibility of contracting a serious illness.