We're told breast screening saves lives. But that is only one side of the picture.
It also results in some women being treated unnecessarily. That treatment could be breast removal or radiotherapy.
For every life saved by screening, more lives are potentially harmed.
So are New Zealand women being told the whole story?
Watch the video for the full 3D Investigates report from Melanie Reid.
For more information on the international research referred to in our investigation, click on the links below:
Canadian research on the absolute benefits of screening: