Over a thousand patients were left on trolleys at Unviersity Hospital Galway during the month of June.
It's the second highest number in the country, and represents an increase of almost 200 patients on the previous month.
Meanwhile, 80 patients spent time on trolleys at Portiuncula Hospital in Ballinasloe during June.
While overcrowding increased at UHG during June, it decreased nationally.
In May, 10,577 patients went without a bed, while last month 9,437 patients were on trolleys throughout the country.
The most overcrowded hospital last month was University Hospital Limerick, with 1,666 patients on trolleys throughout June.
INMO General Secretary Phil Ní Sheaghdha is again criticising the lack of capacity and is calling on the Government to prioritise investment in healthcare infrastructure.
She is also critical of the HSE recruitment freeze, describing it as an 'own goal after own goal'.
