Thousands of NHS workers across England and parts of Northern Ireland have walked out for four hours in a row over pay.
The hospital staff, including midwives, nurses and paramedics, are protesting against the government's decision not to award all NHS workers a 1% pay rise, which was recommended by the NHS pay review body earlier in the year.
The workers, who stressed that "life and limb" services will not be affected, are walking out between 7am and 11am on 13 October.
In addition, the trade union members will not be doing paid overtime and will be taking breaks as part of the industrial action.
"This government's treatment of NHS workers has angered them and this anger has now turned into action," said Dave Prentis, the general secretary of Unison.
"Refusing to pay them even a paltry 1% shows what the government really thinks about its health workers.
"Inflation has continued to rise since 2011 and the value of NHS pay has fallen by around 12%."
But the government has argued that increasing pay for all NHS workers would mean jobs would have to be axed