There are 587 patients waiting on beds in hospitals, according to figures from the INMO's Trolley Watch.
There are 427 patients waiting in the emergency department, while 160 are in wards elsewhere in the hospital.
The number is up on Monday's figure, which was 541. That number, in turn, was up from 456 patients waiting on beds on Friday.
The worst-hit hospitals today are:
The figures come as the HSE and INMO failed to reach an agreement in the Labour Court which would avoid tomorrow's nurses strike.
The president of the Irish Association of Emergency Medicine, Dr Emily O’Connor is calling on the HSE and the Irish Nurses and Midwives Organisation (INMO) to “reach a solution in a sustainable fashion.”
The HSE is expected to announce contingency plans later today ahead of the work stoppage.