Almost 8,000 patients were on trolleys last month, an increase of more than a quarter on August 2016.
The Irish Nurses and Midwives Organisation is meeting with the Health Minister this afternoon to discuss plans to reduce hospital overcrowding this winter.
Patient representative Stephen McMahon is also attending the meeting.
The INMO says 65,455 people were admitted for care in the first eight months of the year but had no bed.
It says this represents a 7% increase on 2016, but a 90% increase on 10 years ago 2007.
These latest figures come ahead of a meeting of the national Emergency Department Implementation Group to discuss the autumn/winter period.
The hospitals which experienced the highest levels of overcrowding in August were:
- University Hospital Limerick: 835 (32 in 2007)
- University Hospital, Galway: 643 (123 in 2007)
- South Tipperary General Hospital: 489 (82 in 2007)
- University Hospital Waterford: 486 (0 in 2007)
- Cork University Hospital: 457 (189 in 2007)
- Midland Regional Hospital, Tullamore: 452 (2 in 2007)
- Mater Hospital Dublin: 436 (315 in 2007)
The INMO says it will be seeking implementation of all emergency measures identified in the taskforce report, including senior clinical decision makers rostered on an extended day basis over the seven days, nurse managers provided with full autonomy to recruit additional staff and for senior general managers to be present in the hospitals on a 24/7 basis.
INMO General-Secretary Liam Doran said: "There is no doubt that the level of attention required to manage trolley overcrowding has dropped in recent months.