More than 7,800 hospital patients did not have a bed in August, according to figures from the Irish Nurses and Midwives Organisation (INMO).
The INMO said University Hospital Limerick had the highest number of patients without a bed this month at 1,215.
Cork University Hospital had the second-highest figure (847), followed by University Hospital Galway (748).
Some 663 patients did not have a bed in Sligo University Hospital, while 536 patients were admitted without a bed in St Vincent's University Hospital in Dublin.
The INMO noted that overall overcrowding figures were lower than last August, though a number of hospitals saw significant increases.
These included Our Lady of Lourdes Hospital in Drogheda (147 patients on trolleys last August compared to 285 in 2024), Mid-Western Regional Hospital in Ennis (28 in 2023 to 151 in 2024) and Beaumont Hospital in Dublin (20 in 2023 to 257 in 2024).
In a statement, the INMO called for an urgent meeting of the HSE's emergency department taskforce to look at the current situation and review lessons learned ahead of predicted surges this winter.
