Non-consultant hospital doctors have voted in favour of industrial action over long working hours, which they say are unsafe for patients and staff.
In the ballot, 1,000 of the Irish Medical Organisation's 2,000 junior doctors voted and 97% have backed industrial action.
The IMO's NCHD group will meet tomorrow to decide on the type of action to be taken.
Three weeks' notice will then be served on the Health Service Executive.
A meeting between the IMO and the HSE is due to take place on Wednesday to discuss contingency measures.
Under the EU working time directive, non-consultant hospital doctors should not be working longer than an average of 48 hours a week.
However, the IMO said some junior doctors are working up to 100 hours a week.
The IMO has promised emergency services will not be affected by whatever action is taken.
The HSE said this evening that it cannot plan for unspecified action and will be seeking clarification from the IMO on its proposed action at Wednesday's meeting.
The executive said it had a National Implementation Group in place to progress compliance with the working time directive.
The group has undertaken site visits to every hospital in the country in recent weeks.
The HSE says many larger hospitals have made significant progress towards compliance, however it recognises that challenges remain in small and medium hospitals and complex speciality settings.