Hundreds of people took part in a protest outside Wick Town and County Hospital on Thursday night.
Holding mobile phone torches and lit candles and standing in silence, the crowd wanted to show its opposition to potential changes to health services.
The protest ended with a piper playing the tune, The Flowers o' the Forest.
On Saturday, similar protests are to be held again in Wick and also Thurso and in Portree on Skye where NHS Highland plans a redesign of hospital care.
Thursday night's protest had supporters from outside Caithness, including Australia, who posted pictures on social media of lit candles.
Highland councillor Struan Mackie, who joined the crowd, said the hospital was "a fantastic facility" for Caithness and north Sutherland.
He added: "The dignified and emotional lighting of candles, lamps and mobile phone torches was a powerful, powerful message."
Nicola Sinclair, a Highland councillor and a founder member of Caithness Health Action Team (CHAT), said she hoped thousands of people would turn up for Saturday's events in Wick and Thurso.
She said large turnouts would send a "clear message" that local communities "do not want to see an erosion of health services".
Among campaigners' concerns about local health services is that an NHS Highland review of hospital provision in Caithness could affect palliative care services in the area.
CHAT believes Wick Town and County Hospital could close and inpatient beds could go at Dunbar Hospital in Thurso.
NHS Highland has said the review was because of an acute staffing problem in all hospitals in Caithness.
It said whatever the future model of care, it would be provided locally.
Meanwhile, last month Health Secretary Shona Robison said NHS Highland needed to improve communication with communities on Skye.
Ms Robison said a special liaison group will be set up to make sure islanders are properly informed about changes to Skye's hospital services.
NHS Highland said on Friday that the Scottish government has approved a request for an external view to look at the arrangements for north Skye in terms of urgent care, minor injury and access to A&E services.