What if, after the Allies won World War II, world health officials had employed a Nazi version of DDT against mosquitoes that transmit malaria? Could that persistent disease, which still infects more than 200 million people a year and kills 400,000 of them, have been wiped off the planet?

That is one of the musings of chemists at New York University who came across an insecticide that had been developed by German scientists during World War II in the course of conducting abstract research on another topic.

It became a historical science mystery.

“Two years ago, we never thought we’d be doing this,” said Michael D. Ward, an N.Y.U. chemistry professor.

In postwar Allied intelligence reports examined by Dr. Ward and his colleagues, German scientists claimed their insecticide, now called DFDT , was more effective than DDT. Allied officials dismissed those assertions as fanciful, especially given the deplorable behavior of Hoechst , the German chemical manufacturer that developed the insecticide , during the war. The company had forced residents of countries occupied by Germany to work in its factories, and it tested drugs on concentration camp prisoners.