There are more than 600 patients waiting for admission to a hospital bed, according to the Irish Nurses and Midwives Organisation.
The Minister for Health has said the number of patients on trolleys is very high and hospitals are extremely busy.
Simon Harris said as a result the Health Service Executive has decided to extend its focus period for the winter plan for two weeks to cope with a surge in hospital attendances since Saturday.
He said health services had always expected the surge to come and everything that can be done is being done to cope with the number of patients on trolleys.
INMO figures show there were 439 patients waiting in emergency departments, while a further 167 were in wards elsewhere in hospitals at 8am this morning.
It is the highest number of patients on trolleys since March 2018, the INMO said.
The hospitals worst affected are University Hospital Limerick with 59 patients waiting, South Tipperary General Hospital, where 50 patients were waiting, and Cork University Hospital, where 48 patients were waiting for admission to a bed.
506 patients were waiting for a bed on the comparable Monday - 15 January - last year.
Official HSE figures say there are 448 people waiting on trolleys, up almost 14% on the same day last year.
Minister Harris and Minister of State for Older People Jim Daly met the HSE Winter Plan Oversight Group to get a briefing on the situation this morning.