Nurses from emergency departments across Ireland are to ballot on possible industrial action, up to strike action.
They say the overcrowding crisis is dangerous for patients and staff.
The Irish Nurses and Midwives' Organisation said that in the first ten months of 2015 almost 80,000 patients admitted to hospital were on trolleys.
Last month nurses in the emergency department at St Vincent's University Hospital began a work-to-rule over the scale of overcrowding.
The hospital is one of the biggest acute facilities in the country.
