More than 3,000 non-consultant hospital doctors will stage a day of action this morning following a long-running dispute with the HSE over working hours.
The move will see members of the Irish Medical Organisation withdraw services from 51 Irish hospitals and it is likely to impact around 15,000 patients through cancelled appointments and procedures.
The strike began at 7am this morning, but doctors have agreed to provide weekend cover for in-patients and emergency care.
The row with the HSE over working hours has been an ongoing issue for many years, but this strike is a dramatic escalation as the first of its kind in 25 years.
The IMO, which has already been through several rounds of talks, has refused to return to the negotiating table until there is a "realistic" proposal on sanctions for hospitals in breach of the EU working time directive.
Dr. Shane Considine, a member of the IMO NCHD committee, said today's strike action aims to improve the quality of care being offered to patients.
"As it stands there's no limitation on the number of consecutive hours a doctor can work," he said.
"And really the whole reason for taking this strike is to provide an environment where doctors are provide care in the optimal setting."
"While I do empathise with patients who may have had procedures or appointments cancelled today, it is ultimately in their best interest that we're taking this action."
The Irish Patients' Association said it was disappointed that there has been no resolution ahead of the strike.
"These issues need to be resolved and resolved urgently," said IPA spokesperson Stephen McMahon. "Because at the end of the day the patient is at the centre of our healthcare system."
McMahon is calling on the Minister for Health James Reilly to personally intervene and call both sides to negotiations.