Forty-three patients were waiting on trolleys at University Hospital Galway – the highest number nationwide – on Wednesday.
Across Ireland yesterday a total of 413 patients were waiting for medical care on trolleys.
The second most overcrowded hospital in the state was Cork University Hospital, with 42 patients stuck waiting.
Last month UHG was the fourth worst in the country, with 457 patients on trolleys recorded over the course of July.
The figures are reported by the Irish Nurses and Midwives Organisation.
The INMO blames staffing issues at busy hospitals around the state for the long waiting times.
Hospitals are in need of more nursing staff in particular – with the HSE estimating over 200 nurses are needed in Ireland to care for all of the patients.