University Hospital Limerick has recorded the highest-ever daily figure of patients waiting on trolleys.
81 people are waiting for a bed there, just a week after a 17-bed ward was closed to facilitate works on a new fracture unit.
The Irish Nurses and Midwives Organisation has launched a petition to have the ward re-opened.
Just under 600 people are waiting in emergency departments and wards around the country.
Over 430 are waiting in the emergency department, while 162 are in wards elsewhere in the hospital.
The worst-hit hospitals today are:
The INMO's Industrial Relations Officer in Limerick, Mary Fogarty said: “Staff and patients are under intolerable pressure in Limerick today. This is the worst-ever figure we've recorded in an Irish hospital.
"This comes less than a week after a 17-bed ward in UHL was shut. The beds that have been closed in UHL need to be reopened immediately.
"We are calling on the Minister to intervene and deal with the chronic overcrowding in the hospital as an urgent matter of patient and staff safety.”