The number of prison suicides in England and Wales fell slightly in 2010 to 58, Government figures have shown.
The Ministry of Justice said that over the 12-month period one female offender and 57 men are thought to have killed themselves while in jail.
The overall figure is down from the 61 apparent suicides recorded in 2009, despite an increase in prison population: it is also the lowest annual number for at least 14 years.
A breakdown of the figures show that four of those who took their own lives in prison during 2010 were aged between 18 and 20, with 54 aged 21 or above.
Justice minister Crispin Blunt said: "Each and every death is a personal tragedy for those who are left behind.
"So any reduction in the number of self-inflicted deaths in our prisons is welcome news.
He added: "It is important to recognise the good work of all those who continue to care for the most vulnerable prisoners in our custody.
"The Government remains fully committed to reducing deaths in custody."
Michael Spurr, chief executive of the National Offenders Management Service, said: "Every death matters and I am extremely grateful to the staff who work so hard to prevent self-harm and suicide.
"That the number of self-inflicted deaths has continued to fall is testament to that hard work."