6,000 psychiatric nurses will begin industrial action this evening.
The Psychiatric Nurses' Association says its member will work only their contracted hours because of health management's failure to address a recruitment and retention crisis.
The PNA says the overtime ban will continue until the issue is resolved.
The HSE says it's putting measures in place to manage the situation.
Its spokesperson, David Walsh, is calling on the PNA to take part in talks at the Labour Court in an effort to resolve the dispute: