Encarsia formosa is a parasitoid used worldwide for the biologicalcontrol of whiteflies on vegetables and ornamental plants grown in greenhouses.Because of outstanding success in controllingTrialeurodes vaporariorumon tomatoes, the biology and behavior of this wasp have been intensivelystudied to identify attributes that contribute to successful biological controland how best to manipulate augmentative releases into greenhouses to suppresswhitefly population growth. In this article, we review the biology of adult andimmatureE. formosa, population dynamics of whitefly-parasitoidinteractions, and commercial use in greenhouses. Deficits in knowledge ofaspects ofE. formosa's biology and use are noted.