Technical Abstract: Apoptosis (programmed cell death) is a tightly regulated physiological process. The inhibitors of apoptosis proteins (IAPs) are key regulators for apoptosis. An inhibitor of apoptosis protein gene IAP1 was recently cloned from Aedes aegypti (AaeIAP1, Genbank accession no. DQ993355), however, it is not clear whether AaeIAP1 is developmentally and environmentally regulated. In this study, we applied quantitative PCR to investigate the expression levels of the AaeIAP1 transcript in different developmental stages and under different environmental conditions. Our results revealed that the expression of the AaeIAP1 transcript was detectable in all life stages of Ae. aegypti, with significantly higher levels in pupal and adult stages than in larval stages. Furthermore, when Ae. aegypti was exposed to stressful environmental conditions (e.g., low and high temperatures, ultraviolet radiation, acetone, and permethrin insecticide treatment), the expression level of AaeIAP1 transcript was increased significantly. Our results suggest that AaeIAP1 might play an important function role in both the physiological development of Ae. aegypti and stress-induced apoptosis.