An estimated 1,000 jobs could be lost at a Devon hospital trust.
The Royal Devon and Exeter (RD&E) Hospital Trust said it is faced with making efficiency savings.
By redesigning services, the trust has estimated it will need fewer staff - about 250 people a year - over the next four years.
It said the posts would be lost through natural wastage. The trust's current workforce is 6,700.
Chief executive Angela Pedder said: "Over the last year we have been working with our partners to understand the likely impact of the efficiency savings that need to be made across Devon.
"Based on our forecasts, we have said to our staff and unions that we anticipate we will therefore need fewer staff - equivalent to around 250 people a year.
"However, with the level of turnover and retirements we have, coupled with a strong commitment to re-skilling and redeploying staff, we are confident that we can meet this challenge without resorting to compulsory redundancies."
Karen Williams, the regional organiser of Unison, told BBC News the union would be "looking very carefully" at the trust's proposals to redesign services.
"We are concerned because reducing staffing by that number- even if it is by natural wastage - could result in a loss of services."
Ms Williams said RD&E staff had received letters in January inviting them to apply for Mutually Agreed Resignation Scheme (MARS).
MARS is an NHS-wide initiative where trusts can offer a severance payment to staff who have been employed for more than a year.
On Tuesday, the chief executive of the Royal Cornwall Hospitals Trust admitted that "several hundred" posts would have to go as it tries to make savings of £27m from its £290m budget.
The trust, which employs about 5,000 people at the Truro hospital, has said it also hopes to avoid compulsory redundancies.