Up to 8,000 people are thought to have gone on a protest against planned changes to emergency and maternity services at a Lincolnshire Hospital.
An NHS cost-cutting plan for Lincs could mean hundreds of job losses and a reduction of some services in Grantham.
The demonstrators gathered in Grantham's Wyndham Park on Saturday to voice their opposition to proposed changes at Grantham Hospital.
Councillor John Hurst, a speaker at the rally, said the cuts were unacceptable.
Millions in overspend
"We don't want cuts because cuts mean the community is subverted.
"The strategic health authority keeps talking about the need to have sustainable services, but what I'm concerned about is a sustainable community and you can't have that without proper public services," said Mr Hurst.
United Lincolnshire Hospitals NHS Trust is trying to tackle a £15m overspend.
Lincolnshire NHS was not available to comment but its preferred option includes cutting back emergency services, closing the maternity centre and stopping all surgery at the hospital except for orthopaedics.
The cuts come as the trust aims to balance its books in line with government targets.