Hundreds of ambulance service personnel have voted in favour of industrial action in an ongoing dispute with the HSE.
The National Ambulance Service Representative Association said 98% of its members "voted overwhelmingly" to back the move in a dispute over representation rights and the deduction of union subscriptions from payroll.
The dispute centres around the HSE's refusal to recognise NASRA, an affiliate of the Psychiatric Nurses Association that was established in 2010.
Around 500 Emergency Medical Technicians are NASRA members.
The union said it will be writing to the HSE in the coming days.