Maori women continue to have the highest rates of breast cancer and the gap between them and other New Zealand women is growing, a study by the University of Otago shows.
The difference has increased from 7% between 1981 and 1986 to 24% in 2001 and 2004.
The study shows breast cancer rates in Maori have increased 70% compared with 50% for non-Maori over two decades.
Senior research fellow Ruth Cunningham says they are unsure of the reasons behind the growing gap and can only speculate.
Dr Cunningham says one would expect Maori to have lower rates than European women because they give birth earlier and have more children, which normally reduces breast cancer rates.
She says more research needs to be done, but in the meantime, more Maori women should be screened.