The government is preparing to issue new rules that will make it substantially easier for veterans who have been found to have post-traumatic stress disorder to receive disability benefits, a change that could affect hundreds of thousands of veterans from the wars in Iraq, Afghanistan and Vietnam.

The regulations from the Department of Veterans Affairs, which will take effect as early as Monday and cost as much as $5 billion over several years according to Congressional analysts, will essentially eliminate a requirement that veterans document specific events like bomb blasts, firefights or mortar attacks that might have caused P.T.S.D., an illness characterized by emotional numbness, irritability and flashbacks.

For decades, veterans have complained that finding such records was extremely time consuming and sometimes impossible. And in the wars in Afghanistan and Iraq, veterans groups assert that the current rules discriminate against tens of thousands of service members  many of them women  who did not serve in combat roles but nevertheless suffered traumatic experiences.

Under the new rule, which applies to veterans of all wars, the department will grant compensation to those with P.T.S.D. if they can simply show that they served in a war zone and in a job consistent with the events that they say caused their conditions. They would not have to prove, for instance, that they came under fire, served in a front-line unit or saw a friend killed.