P: OPER HPMlnIreon Crp 30575489 D.v Spec Pags doc-2A/72008 This invention relates to the field of biotechnology or genetic engineering. Specifically, this invention relates to the field of gene expression. More specifically, this invention 5 relates to a novel ecdysone receptor/chimeric retinoid X receptor-based inducible gene expression system and methods of modulating gene expression in a host cell for applications such as gene therapy, large-scale production of proteins and antibodies, cell based high throughput screening assays, functional genomics and regulation of traits in transgenic organisms.