Nursing Assistants and maternity support workers at Surrey and Sussex Healthcare NHS Trust are taking part in further industrial action this week.
The strike action started yesterday and will continue until Thursday.
This is the third time Unison Union members have taken industrial action in a dispute over back pay, after the Trust offered to change their salary band. Unison said there has been progress in negotiations but a satisfactory offer on back pay had not been received.
The Trust, which runs East Surrey Hospital, advises patients with scheduled appointments to attend unless informed otherwise.