The European Central Bank is examining ditching the €500 note, its president has said.
Mario Draghi described the note used by savers to hoard tens of billions of euros as an instrument also used by criminals.
Mr Draghi said savers would not be penalised and could use the €200 note instead to hold their cash.
"People will continue saving the €200 notes," Mario Draghi told lawmakers in the European Parliament, saying that governors were considering action.
"The €500 note is being viewed increasingly as an instrument for illegal activities," he said. "It has nothing to do with reducing cash."
The amount of cash in the euro zone rose to more than €1 trillion last year, with almost 30% of it hoarded in €500 notes, reflecting fears about banks as well as exasperation with low returns on savings.
European finance ministers called on the ECB on Friday to look at ways to tighten access to the notes as part of a move to cut funding of militant activity. It is more than five times the value of the largest US note - the $100 bill.
Germany was one of the early champions of the €500 note to match the value of its old 1,000 mark note and cater to Germans' traditional preference for cash over electronic money.
Cash hoarding has become more prominent throughout the years of crisis. Capital controls prohibit large withdrawals in Greece, where savers have hoarded tens of billions, after big depositors lost money in the country's financial bailout.
Meanwhile, one of the world's biggest banknotes - the 1,000-Swiss franc bill - is here to stay, the central bank said today, despite consultations overscrapping the European Union's highest denomination to keep it out of the hands of militants.
A Swiss National Bank (SNB) spokesman said there were no plans to follow Europe's lead over Switzerland's bill which is worth almost twice the value of the €500 note and ten times the biggest US denomination, the $100 bill.
The bank's policy, he added, was that the size of a banknote had no impact on efforts to combat crime.
Few Swiss have seen one of the violet 1,000-franc notes, the latest version of which features the portrait of 19th century cultural historian Jacob Burckhardt.
According to SNB figures, 38.3 billion francs of them were in circulation in 2014, accounting for just under 10% of Swiss banknotes but 61% of the total value of cash in paper form.
"The high proportion of large denominations indicates that banknotes are used not only as a means of payment but also to a considerable degree as a store of value," the SNB website said.
Banknote circulation rose to 62.7 billion francs in 2014.
"The increased demand for banknotes is due to the persistently low level of interest rates. The greater demand for small-denomination notes mainly reflects positive developments in private consumption," the latest SNB annual report said.
One Swiss banking source said they had seen recent signs of people hoarding 1,000-franc notes as a reaction to negative Swiss interest rates that make banks and large institutional investors pay for some deposits.
