The Ministry of Defence (MoD) is to award £3m in compensation to 360 veterans of Cold War experiments at the Porton Down research centre.
The government has not admitted liability
Defence minister Derek Twigg said: "The government sincerely apologises to those who may have been affected."
The money is "in full and final settlement" of claims and without admission of liability, Mr Twigg added.
Many of those given nerve agents in the trials at the Wiltshire complex have complained of life-long ill health.
The servicemen were often told they were helping to find a cure for the common cold.
The settlement in the long-running dispute between the government and victims of the trial was "amicable" and the "best result", Mr Twigg added.
Alan Care, the lawyer who has acted for many veterans over the past decade, said: "I think this is a good deal for them
"A lot of veterans wanted the apology - the money was an add-on. I would commend the MoD at this point, be it late in the day.
"The government is facing up to its Cold War past."
He said there was "100% unanimous" acceptance of the deal, and rejected claims some veterans had been pressured into it.
Ken Earl, survivor and founder of the 536-member Porton Down Veterans' Support Group, said: "I am pleased that at long last there has been a settlement.
The 74-year-old added: "It will allow our members to have a degree of closure on this issue and get on with their lives.
"But from the money point of view it should have been a lot more. It's not even half the price of a tank by today's standards."
Mr Twigg said: "The government accepts that there were aspects of the trials where there may have been shortcomings and, where, in particular, the life or health of participants may have been put at risk.
"The Ministry of Defence is grateful to all those whose participation in studies at Porton Down made possible the research to provide safe and effective protection for UK Armed Forces."
He said any veterans unhappy with the £8,000 individual settlement could also apply for compensation under the War Pensions' scheme.
Ronald Maddison died in 1953
Between 1939 and 1989, hundreds of servicemen took part in experiments at Porton Down.
Many were given forms of the sarin nerve agent developed by the Nazis in World War II and say they have suffered a lifetime of ill-health as a result.
Only one other Porton Down case has resulted in compensation.
That was for 20-year-old aircraftsman Ronald Maddison, of Consett, County Durham - who Mr Earl was at Porton Down with.
In 1953, Mr Maddison volunteered to take part in what he believed to be a test for a cold cure.
Within an hour of having sarin dabbed on his arm at the Salisbury Plain laboratory, he was dead.
The MoD eventually paid £100,000 in compensation to Mr Maddison's family but only after mounting an unsuccessful legal challenge against a 2004 inquest verdict which ruled he had been unlawfully killed.
The review, led by independent assessor Professor Sir Ian Kennedy, concluded that some trials at the centre from the 1940s to the 1970s involved "serious departures" from the ethical standards that should have been observed.
Mr Earl said: "I was in the same test as Ronald and haven't been well all my life and believe it damaged my nervous and immune system.
"What they put on my skin was the most deadly compound ever manufactured by man - sarin nerve gas - which is now described as a weapon of mass destruction."
Porton Down was established in 1916.