For demonstrating the signaling properties of nitric oxide, he was co-recipient of the 1998 Nobel Prize in Physiology or Medicine with Robert F. Furchgott and Ferid Murad.

Ignarro has also previously worked as a staff scientist, research department, for the pharmaceutical division of CIBA-GEIGY Corporation in New York.

[6][7] Ignarro has published multiple books for lay audiences about health and wellness focusing on the benefits of increasing nitric oxide production.

After Geigy merged with Ciba Pharmaceuticals, Ignarro decided to move back to the world of academia, this time as a professor.

[10] Ignarro's research demonstrated that nitric oxide serves the functions of vasorelaxant and inhibitor of platelet aggregation, with both effects mediated by cyclic GMP.

In 1984 he realized that the properties of nitric oxide were the same as those seen in the endothelium derived relaxing factor (EDRF) previously identified by Robert Furchgott three years earlier.

[5] During the decades since Ignarro and Furchgott's initial research, thousands of studies have been published about the effects of nitric oxide as the endothelium derived relaxing factor.

This has led to the development of erectile dysfunction drugs such as Viagra and nutritional supplements designed for cardiovascular health and athletic performance.

In 1985, Ignarro moved from New Orleans to Los Angeles where he accepted a position at the UCLA School of Medicine and continues to research and teach.

Ignarro first worked with Herbalife to develop Niteworks, a dietary supplement designed to boost the body's own production of nitric oxide.

[14] While testifying before Congress in 2000, Ignarro remarked: "Only in America could the son of an uneducated carpenter receive the Nobel Prize in Medicine".