Zerhouni has been at the helm of the research organization since 2002 and was most noted for establishment of the NIH Roadmap for Research, a program that improved collaboration on major projects among the NIH's 27 separate institutes.

"Over the past six years, we experienced a revolution in the biomedical sciences and I feel fortunate to have been part of it," Zehouni said in a written statement.

There was no official word on a replacement for Zehouni, an Algerian immigrant whom The New York Times said became a self-made millionaire by inventing medical devices while working as a radiologist at Johns Hopkins University.

The Times said that Zehouni's tenure had its ups and downs. He arrived at a time when Congress was pumping up the NIH budget; however it has remained largely flat since then. In addition, he raised the ire of many NIH researchers with his 2005 order banning them from doing outside consulting work for drug companies.