The Irish government has acted to shore up its financial system.
It is guaranteeing all deposits in Irish banks and all money borrowed by the banks from other financial institutions.
On Tuesday, the Department of Finance said the state would safeguard all deposits, bonds and debts in six banks and building societies for two years.
The decision follows Monday's enormous slide in the value of the shares of Irish banks.
The banks covered are Allied Irish, Bank of Ireland, Anglo Irish Bank, Irish Life and Permanent, Irish Nationwide Building Society and the Educational Building Society.
The Department of Finance said all deposits, bonds and debts in the six banks and building societies would be covered by the state for the next two years. But there will be terms and conditions.
That means that the Irish government has decided that the Irish taxpayer will now provide a guarantee for up to 400 billion euro of liabilities.
The Irish stock exchange reacted favourably to the move with banks shares rising dramatically after big falls on Monday.
The Northern Bank and Ulster Bank have moved to reassure depositors about their stability and credit-worthiness.
Neither are covered by the Irish government guarantee, but both have issued statements intended to reassure customers their money is safe.
The Northern, owned by the Copenhagen based Danske Bank, emphasises it is part of a strong and solid European banking group with a very strong credit rating.
Ulster Bank has pointed out that it is owned by the Royal Bank of Scotland - one of the largest banks in the world in which shareholders recently invested an additional 12 billion pounds in capital.