The World Health Organization (WHO) has reversed a 30-year policy by endorsing the use of DDT for malaria control.
The chemical is sprayed inside houses to kill malaria-carrying mosquitoes.
DDT has been banned globally for every use except fighting disease because of its environmental impacts and fears for human health.
WHO says there is no health risk, and DDT should rank with bednets and drugs as a tool for combating malaria, which kills more than one million each year.
"The scientific and programmatic evidence clearly supports this reassessment," said Dr Anarfi Asamoa-Baah, WHO assistant director-general for HIV/AIDS, TB and Malaria.
"DDT presents no health risk when used properly"
"Indoor residual spraying is useful to quickly reduce the number of infections caused by malaria-carrying mosquitoes; it has proven to be just as cost effective as other malaria prevention measures, and DDT presents no health risk when used properly."
Teams of sprayers typically visit endemic areas once a year, spraying the chemical on the inside walls of houses; mosquitoes landing there absorb it and die.
A potent insecticide, DDT fell into disrepute with the publication of Rachel Carson's Silent Spring just over 40 years ago.
The book showed that widespread, indiscriminate use of DDT and related compounds was killing wildlife over vast tracts of North America and western Europe.
A number of countries banned it, and in 2004 the global treaty on Persistent Organic Pollutants (POPs) made the prohibition global - except for a clause allowing its manufacture and use in disease control.
Some African countries have continued to use it, though most have either switched to other kinds of insecticide or pursued a strategy of issuing insecticide-impregnated bednets. Some aid agencies have policies of not funding programmes involving DDT.
South Africa was one country that switched, but it had to return to DDT at the beginning of the decade after mosquitoes developed resistance to the substitute compounds.
"Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT," said Arata Kochi, director of the WHO's Global Malaria Programme.
Richard Tren of the pressure group Africa Fighting Malaria has been campaigning for DDT's rehabilitation.
"All development agencies and endemic countries need to act in accordance with WHO's position on the use of DDT for indoor residual spraying," he said.