Cork University Hospital was the second most overcrowded hospital in the country last month.
A report from the Irish Nurses and Midwives Organisation shows that just under ten thousand patients went without a bed in Irish hospitals in June, including 1059 patients in CUH, and 370 patients in the Mercy Hospital.
The figure for CUH is almost double last years total of 673.
The INMO are calling on the HSE to take urgent action on the rising trolley figures, saying it was "a June like no other".
