Hundreds of staff at council-run residential care homes across Glasgow are expected to take part in two days of strike action starting today at 10pm.
Members of trade union Unison voted for the action because they want to stop the council changing their job roles, which may mean pay cuts and moving to new shifts of more than 12 hours.
The council says staff have already agreed to the changes and it meets their needs for more weekends off.
In another blow to the council, Unison said they would not be providing an emergency "life and limb" service during industrial action.
It has prompted fears over the safety of residents in Glasgow's 15 homes for the elderly and a home for people with physical disabilities.
Strikers will form picket lines outside the buildings.
Among the homes affected are Fulton Lodge in Easterhouse, Drumry House in Drumchapel, and Windlaw House in Castlemilk.
Unison Glasgow branch secretary Brian Smith said the decision to strike was a tough one for members.
He said: "We haven't had a strike at an elderly care home for around 20 years - nobody wants to be in this position.
"But some of our members have an issue with working the 12-hour shifts and the new staffing structure means some people will have their pay cut.There are also concerns over staff being made to administer medicine."
Mr Smith warned there was a possibility of more action: "If the council will not come back around the table then clearly we will have to look at what further action we take."
As the Evening Times reported last week, council bosses have been working with the Scottish Care Inspectorate on a contingency plan for the 48-hour action.
Workers could be drafted in from other social care sections of the council. A council spokesman said: "Contingency plans have been drawn up and we are hopeful the service will operate as close to normal as possible.
"We have been very surprised that Unison has refused to offer 'life and limb' cover, just as we are very disappointed that Unison has moved to strike action at all."
The strike follows walkouts by Pupil Support Assistants (PSAs) who support pupils with complex needs last year.
Susan Aitken, the SNP Group's social care spokeswoman said: "Social work management must sit down and talk with trade union representatives now and work to reach an agreement."