The eradication of yellow fever in Havana, Cuba, was achieved by a fruitful collaboration between American and Cuban physicians. Carlos Finlay, a Cuban physician who proposed the mosquito-vector theory in 1881, shared his ideas, his publications, and a sample of mosquito eggs with the U.S. Army Yellow Fever Commission. The commission, headed by MAJ Walter Reed, used human volunteers to confirm Finlay's theory. MAJ William Gorgas adopted mosquito-control measures in his sanitation program and, within 6 months, yellow fever was controlled in Havana for the first time. Finlay held fast to his ideas despite incredulity and ridicule. His tenacity and scientific honesty vindicated his ideas about yellow fever.