 Aedes aegypti and Aedes albopictus are two of the most common mosquito species in the world, and they are also responsible for transmitting several serious diseases such as chacongania, dengue, rift valley fever, yellow fever, and Zika virus. These mosquitoes are also known to be highly resistant to many types of insecticides, which makes controlling their populations difficult. Insecticide resistance has been observed in both species in various parts of the world, including North America, South America, Africa, and Asia. Resistance can occur through target site mutation or increased detoxification of the insecticide. Geographic distributions of the different mechanisms of resistance are not yet fully understood, but it is clear that more research needs to be done to better understand how resistance is developing and spreading. This article was authored by Katharine Elmoise, John Vontes, Ademir J. Martens, and others.