A new report says 308 patients were harmed or could have been harmed by mistakes made in public hospitals in the past year.
The latest report on so-called Serious and Sentinel Events in hospitals says 92 of those people died in hospital or shortly afterwards, although not necessarily as a result of the error.
The total number of patients affected has increased by 50, and the mistakes mainly concern clinical management failures, falls and suicides.
The report, which covers the period to June this year, was released by the Government's quality improvement committee on Monday.
It covers all district health boards and concerns errors which did, or could have, resulted in disability or death unrelated to the patient's illness.
Clinical management issues involving diagnosis or delayed or inadequate treatment were behind almost 40% of all incidents. Falls came next at 27%, followed by suicide at 12%.
Increase due to more reporting
Experts say the number of patients caught up in preventable mistakes is rising because hospitals are being urged to report events so the sector can learn from them.
They point out the figures amount to just three out of every 10,000 people admitted to hospital, and that measures are under way to boost patient safety in the most at risk areas.
Doctors and public health experts have welcomed the report.
The principal medical officer at the Health Ministry, David Galler, says any errors are tragedies for the families of those involved.
"Our sympathy and our condolences and our apologies go out to each and every one of those people and their families who have had an adverse outcome as the result of a preventable error in one of our hospitals."
But Dr Galler says the focus should not be on the numbers.
"The purpose of this report is for national learning."
Dr Galler says more than 1800 district health board staff have been trained in the reporting of the events.
