Since viral pathogens represent a significant threat to human health, a better understanding of the cellular factors that impact infection would facilitate the development of therapeutics. The recent advent of RNA interference (RNAi) technology coupled with the ease and efficiency of RNAi in Drosophila cell culture has led to the widespread use of this experimental system for high-throughput RNAi screening of host factors required for viral infection [Cherry et al., Genes Dev 19:445-452, 2005; Hao et al., Nature 45:890-893, 2008; Sessions et al., Nature 458:1047-1050, 2009]. Here, we describe the use of this system for the identification of host factors that impact viral infection.