This invention relates to the field of biotechnology or genetic engineering.Specifically, this invention relates to the field of gene expression. Morespecifically, this invention relates to a novel ecdysone receptor/chimericretinoid X receptor-based inducible gene expression system and methods ofmodulating gene expression in a host cell for applications such as genetherapy, large-scale production of proteins and antibodies, cell-based highthroughput screening assays, functional genomics and regulation of traits intransgenic organisms.