There were 623 patients on trolleys, or on wards, waiting on admission to a hospital bed, according to figures from the Irish Nurses and Midwives Organisation.
This includes ten children waiting at the Children's University Hospital, Temple Street in Dublin, and four at Our Lady's Children's Hospital, Crumlin.
The worst affected hospitals were Cork University Hospital with 58 patients waiting and 55 at University Hospital Limerick.
Other hospitals badly affected are Letterkenny General Hospital with 43 patients on trolleys, University Hospital Kerry with 35 and the Midland Regional Hospital, Tullamore, with 34 patients waiting.
There has been a small rise of over 4,100 people on national waiting lists for hospital care, putting the total in January at over 693,890, according to figures by the National Treatment Purchase Fund.
The figures for January compare with 689,700 waiting the previous month.
Of those waiting to be seen or treated in January 98,500 were waiting for inpatient, or day case treatment.
There were also 27,332 waiting for a gastrointestinal check.
Over 502,400 were waiting to be seen by a consultant at an outpatient clinic.
A further 65,500 people were scheduled for follow-up care soon, having had initial treatment already.