The first long-term study in Australia of Indigenous mortality rates has found a massive fall in deaths among children in the Northern Territory up to the age of four.

But chronic disease remains a serious issue.

The study, involving Darwin and Canberra-based researchers, looked at figures in the Northern Territory dating back to the 1960s.

It shows the overall mortality rate has fallen, with a 30 per cent fall in female deaths and an 85 per cent drop for children up to four-years-old.

Death from infectious disease also fell 62 per cent.

But Dr John Condon, from Darwin's Menzies School of Health Research, says the rate does not match the fall in the overall Australian population.

"The gap between Indigenous and non-Indigenous Australians has increased in death rates, in the Northern Territory at least, and that's a tragedy," he said.

"Australia can achieve improvements in health gains, has done over the last 40 years, but for the part of our population with the worst health status we haven't been able to even share in the general health gains."

Dr Condon says the death rate from chronic disease, such as diabetes, has not changed.

He says the prevention of chronic disease is a key issue for Indigenous Australians.

"It really does focus attention on problems of nutrition, of exercise, of the high level of smoking in the Northern Territory in Indigenous and non-Indigenous people," he said.

"It really should focus attention on ways to prevent those diseases occurring."