Around 80 radiographers across the Bay of Plenty and Lakes districts have walked off the job causing disruption in local hospitals.
The action is part of a nationwide strike of nearly 1100 radiographers employed by district health boards around the country after nine months of failed negotiations between the union and DHBs.
The 24-hour strike started at 7am this morning and another strike is planned for Wednesday.
More than 300 appointments were going to be disrupted as a result of the industrial action.
A Bay of Plenty District Health spokesman said 47 staff were expected to strike.
The Lakes district normally had 26 MITS working across both Taupō and Rotorua hospitals, with almost all expected to strike, according to a statement from the Lakes District Health Board.
Apex national secretary Deborah Powell said 54 Bay of Plenty District Health Board union members and 27 Lakes District Health Board members were set to strike.
Procedures radiographers, also known as medical imaging technologists, perform include x-rays, CT and MRI scans.
The planned strike action was the third and fourth strike in the last month and will involve a complete withdrawal of labour.
Powell said at the end of the day the union was doing what they had too to get negotiations settled.
She said the union had grown "frustrated" with bargaining and were working to get an offer locked down that addressed staff shortages, low worker retention and unsustainable hours.
Radiographers across the country were becoming "burnt out" in their roles, with many choosing to jump ship to the private sector, she said.
Further strike action was already on the cards for the coming weeks unless an offer was reached.
Health services that required imaging would need to be significantly reduced for both Rotorua and Taupō hospitals.
The Lakes District Health Board had reached an agreement with the union about the provision of life preserving services for both strikes.
Bay of Plenty District Health Board surgical services business leader Bronwyn Anstis said it was estimated that around 300 radiology diagnostic procedures would be affected or displaced by the industrial action.
She said six operations had also been affected and 59 outpatients' appointments had to be rescheduled.
A Lakes District Health Board spokeswoman said no elective procedures had to be cancelled today due to the strike, but people were warned to expect delays in the emergency departments.
Information on further strike action would come out in the next week or so.