Known for his research in the field of pharmacology, he received the 1998 Nobel Prize in Physiology or Medicine for his work on nitric oxide. In 1985, he joined the faculty of the University of California, Los Angeles' School of Medicine.
He earned his Bachelor of Science and Doctor of Philosophy degrees in pharmacology from, respectively, Columbia University and the University of Minnesota.
He taught for over a decade at Tulane University's medical school and founded an organization called the Nitric Oxide Society.
He was raised in New York City by Italian immigrant parents. He and his wife later settled in Southern California.
He and Gertrude B. Elion were both recipients of the Nobel Prize in Physiology or Medicine; Elion received the honor in 1988, and Ignarro shared the 1998 prize with biochemist Robert F. Furchgott and fellow pharmacologist Ferid Murad.