University Hospital Galway was the third most-overcrowded in the country during last month, according to new figures from the INMO.
During the month of February, 805 patients were treated on trolleys at the Galway hospital - with Limerick and Cork University Hospitals being the most overcrowded.
The figures show over 10,000 admitted patients were left on trolleys across the country during February - an increase of 23% on February 2019.
At Mayo University Hospital, 317 were on trolleys during last month - up from 171 in the same month last year.
290 patients were treated on trolleys at Sligo University Hospital - which was down on the figure for Feb 2019 - while the figure at Portiuncla Hospital was much the same.
The Irish Nurses & Midwives Organisation says the long-running trolley crisis has to be the top priority in talks on forming a new Government.
The INMO says their members are forced to provide care in appalling conditions, while qualified healthcare staff are queueing ujp to work, but hospitals are unable to hire them.
The union is calling for the recruitment embargo to be lifted - whatever the make up of the next Government.