About 9,000 nurses in Northern Ireland are to launch 12 hours of strike action at 08:00 GMT on Wednesday morning.
They belong to the Royal College of Nursing (RCN), which has not participated in strike action in its 103-year history.
Alongside the other health unions, they are protesting over pay and patient safety. Other nurses, who are members of Unison, will also be walking out.
Pat Cullen from the RCN said: "No time is a good time to strike, but years of negotiations between various health ministers failed and years of warnings were ignored." The RCN plans to stage picket lines in hospitals across Northern Ireland.
According to the RCN, nurses' pay within the health service continues to fall behind England, Scotland and Wales. It argues that the real value of nurses' pay here has fallen by 15% over the past eight years. There are just under 2,800 unfilled nursing posts within the health service in Northern Ireland. The RCN estimates that a similar level of unfilled posts exists within nursing homes.
The nursing vacancy rate in Northern Ireland is 13%. This means that for every eight nurses who should be working in Northern Ireland, one is missing.
Nurses are demanding better workforce planning. Last year, the local health service spent £52m on agency nurses to fill these gaps in the workforce. That money, the RCN argues, could be better managed to train and pay health service nurses.