We sequenced and characterized the inhibitor of apoptosis (iap) 1 gene from Aedes albopictus, designated as Aaiap1. The Aaiap1 gene rescued Spodoptera frugiperda (Sf9) cells from apoptosis when cotransfected with the Drosophila pro-apoptotic hid gene. The antiapoptotic function of the Aaiap1 gene was evaluated in the bluetongue virus (BTV)-induced apoptosis system. BTV infection induced apoptosis in vertebrate cells via the intrinsic apoptotic pathway. This was shown by the translocation of cytochrome C and the second mitochondria-derived activator of caspase (Smac, also known as DIABLO) from the mitochondria and the subsequent activation of caspase-9 and -3. Stable expression of the Aaiap1 gene in derivative baby hamster kidney cells delayed BTV-induced apoptosis by 24 h and reduced the BTV progeny yield by 10-fold. This study provides the first evidence that the mosquito AaIAP1 protein possesses antiapoptotic activity. © 2007 The Authors Journal compilation © 2007 The Royal Entomological Society.