Workers at two Adelaide hospitals will walk off the job as rolling stoppages continue in support of a new enterprise agreement.
The workers, including orderlies, cleaners and kitchen staff, at the Flinders Medical Centre and the Strathalbyn Soldiers Memorial Hospital, are members of United Voice.
They will attend stop-work meetings on Friday as the union says statewide industrial action is possible if an agreement can't be reached.
It wants a new deal to include a commitment of no further outsourcing of jobs, a fair wage increase and measures to address staff shortages.
"Failing to address these critical issues will have grave impacts on public health services and our members' jobs," United Voice branch secretary David Di Troia said.
"United Voice members are staying strong and standing together to achieve jobs they can count on."
The latest industrial action follows a move by public hospital doctors to also walk off the job on Thursday in support of a new pay deal.