Spain is about to discover whether 100 billion euros of emergency EU money is enough to bail out its crippled banks.
Independent auditors from the US and Germany have been studying bank balance sheets that have been hit by a collapsed property boom in the eurozone's fourth largest economy.
There are already doubts that the EU money set aside will be enough and market relief lasted only an hour after the bailout request was announced.
The audit has been carried out by consultants Oliver Wyman and Roland Berger and is the second of three reports.
The third is still expected to be published at the end of July, despite reports suggesting it would be delayed until September.
Almost two weeks ago, Spain's government asked the EU for money to help prop up its beleaguered financial sector.
Although they haven't agreed on an amount yet, the eurogroup of 17 nations has offered up to 100 billion euros and it is widely thought that Spain will need all that and maybe more.
Forecasts of how much Spanish banks might need vary widely.
The IMF said they would require about 40 billion euros but JP Morgan has estimated 75 billion, as part of a wider package that would cost 350 billion.
This, however, would be consistent with the trend set by previous European bailouts.
Greece and Portugal both required additional money after the initial injection of cash, but Europe has insisted that it will give Spain the money it needs and a little bit more to cover unforeseen circumstances.
The interest rate that the Spanish government has to pay on 10-year borrowing has twice climbed above the psychologically important 7% mark in recent weeks.
It is proof that Spain's fortunes, rather than Greece's, are key to the future of the single currency.
Francois Hollande, the new French president, has said that the high borrowing costs for Spain and Italy are unacceptable and Europe must show "a much faster ability to intervene".
That intervention might come via the two Euro bailout funds: The EFSF and ESM.
Journalists at the meeting of the G20 in Los Casbos, Mexico, were briefed that a plan mooted by the Italian PM Mario Monti might be implemented.
It would allow the EFSF and ESM to directly buy Spanish and Italian sovereign bonds in the hope that such action would help bring the yields (interest rates) down.
That would require approval from Germany which has so far been opposed to such measures - although it is likely to be discussed further when Angela Merkel meets Mario Monti, Francois Hollande and Spanish PM Mariano Rajoy in Rome on Friday.
It could be announced officially at an EU leaders' summit in Brussels at the end of next week.
Spain looked to raise 2bn euros at a sale of 2, 3 and 5-year bonds today and managed to easily secure that sum but the rates demanded for the bonds maturing in 2014, at 4.7%, were more than double those paid in March.