Alphavirus transducing systems (ATSs) are important tools for expressing genes of interest (GOI) in mosquitoes and nonvector insects. ATSs are derived from infectious cDNA clones of mosquito-borne RNA viruses (family Togaviridae). The most common ATSs in use are derived from Sindbis viruses; however, ATSs have been derived from other alphaviruses as well. ATSs generate viruses with genomes that contain GOI's that can be expressed from additional viral subgenomic promoters. ATSs in which an exogenous gene sequence is positioned 5' to the viral structural genes is used for stable protein expression in insects. ATSs in which a gene sequence is positioned 3' to the structural genes is used to trigger RNAi and silence expression of that gene in the insect. ATSs are proving to be invaluable tools for understanding vector-pathogen interactions, vector competence, and other components of vector-pathogen amplification and maintenance cycles in nature. These virus-based expression systems also facilitate the researcher's ability to decide which gene-based disease control strategies merit a further investment in time and resources in transgenic mosquitoes.