The Beckman Coulter factory in Galway is to close with the loss of 140 jobs.
The company has said up to 80 staff will be offered redeployment at its facility in Co Clare.
Workers were called to a meeting at the company's Galway base this morning.
Beckman Coulter is involved in the medical diagnostics sector and has had a presence in the city for more than 40 years.
It manufactures reagents and rotors, which are used in hospital equipment.
The company has said it is scaling back some production and moving other product development elsewhere.
Beckman Coulter describes itself as one of Ireland's longest established multinational companies.
It also operates a plant in O'Callaghan's Mills in Co Clare.
Beckman Coulter says the decision to close its plant in Galway follows a review of the company's operations.
Production will be transferred to other locations, with the bulk of Galway manufacturing moving to Co Clare and other production switching to the US.
A company spokesperson said 70 to 80 jobs would be available for staff who wished to redeploy to the Beckman Coulter facility at O'Callaghans Mills, near Tulla.
Incentives will be offered to staff to encourage them to take up this option.
Negotiations on redundancy packages for other workers will get under way next week.
The company makes reagents for use in medical diagnostics.
These are chemicals that are mixed with samples to allow for laboratory testing.
Rotors that are used in diagnostic machinery are also made in Galway.
Production in Galway will be phased out over the next 15 months and the facility will close by the end of next year.
Staff leaving the plant after today's announcement did not comment. Many have worked at the company for over 30 years.
SIPTU, which represents around half of the workers, says the decision, while not entirely unexpected, was a shock to many of the employees.
The union says it is regrettable that a highly profitable company has decided to take such action to further maximise revenues.
It says the closure of the Mervue plant will have a serious and severe impact on the region.
Galway Chamber of Commerce said that the announcement was a blow for the city.
Its President, Frank Greene, expressed hope that other medical companies in Galway would have employment opportunities for Beckman Coulter workers who were losing their jobs.
The IDA said it would work to find new occupants for the plant, which is located in Mervue Business Park.