4,000 health workers from two trade unions in Northern Ireland - Unite and the GMB - took part in a three and a half hour strike as part of a dispute over pay.
Midwives, nurses, and ambulance staff in England are also involved in the dispute.
It was the first such strike by NHS staff over pay in more than 30 years.
The Northern Ireland workers are protesting outside Stormont and urging the power-sharing executive to sanction a 1% pay increased that has already been awarded to their colleagues in Scotland.
