Nearly 13,000 nurses across Finland are threatening to resign next month in a pay row, trade union officials say.
Finland's nurses complain of poor pay and huge workloads
The Union of Health and Social Care Professionals (Tehy) is demanding a 24% wage increase for its members over 28 months, rejecting employers' 12% offer.
Tehy says half of its 124,000 staff are struggling to survive because of low pay, and many now want to work abroad.
If no compromise is found, the mass resignations will cripple Finland's healthcare system, the union warns.
Tehy's Jaana Reijonaho told the BBC News website that 12,800 members would quit on 19 November if their demand for higher wages was not met.
"Hospitals will be paralysed, especially big ones where many of our members are employed," Ms Reijonaho said.
Nurses in Finland's public sector say they are poorly paid and often have to cope with huge workloads.
A nurse's average salary is about 1,900 euros (£1,324), compared to 2,300 euros (£1,602) average pay for full-time workers across the country, Ms Reijonaho said.
"Half of our members have to survive on that money. It's not easy," she said.
"Thousands have moved to Sweden and especially Norway since the 1990s because salaries there are so much better," she added.
But employers say a 24% pay rise is unjustified, as it is about 15% above average wage growth.
The mass resignations will be the biggest industrial action in Finland's recent history if no compromise is found at ongoing talks between the two sides.
Tehy says it is "extremely sad that trained healthcare personnel have to defend their justified aims in such a drastic manner".
Some experts, however, say the 12,800 signatures collected by Tehy could not be accepted as resignation letters from a legal point of view.
The union admits that this is something of a grey area.
"The situation is not clear. A court case is possible," Ms Reijonaho said.