There are 580 patients waiting for beds in hospitals around the country this morning, according to the INMO Trolley Watch.
The INMO said 429 are waiting in emergency departments, while another 151 are in wards elsewhere in the hospitals.
The worst-hit hospitals today are University Hospital Limerick with 54 people awaiting beds.
This is followed by University Hospital Galway which has 50 patients on trolleys and Cork University Hospital with 47 waiting for beds.
The INMO yesterday criticised plans by University Hospital Limerick to close an in-patient ward. There are 17 beds in the ward that are used primarily to treat patients who require short periods of admission.
INMO industrial relations officer for Limerick, Mary Fogarty, said losing beds at the most overcrowded hospital in the country, "will only worsen Limerick's overcrowding crisis".