Medical physicists providing essential radiation services to cancer patients throughout the country have voted for a partial strike over five days.

It follows four months of failed wage negotiations.

Their APEX union advocate David Munro says they've been offered a one percent increase for the current year - and that's in a proposed three year contract.

The union wants salaries to be increased by four percent every six months for the next two years.

The strike's set down for Wednesday 27th May and will run through to Sunday 31st May.

The medical physicists in the Wellington, Waikato, Auckland, Canterbury and Southern DHBs will refuse to do any overtime on those days.

Staff at mid-central DHB will refuse to work on one machine during the strike.