Intracellular pathogens represent a serious threat to human health. Although the biology and the virulence factors involved in intracellular bacterial infection are relatively well documented, little is known about the host factors involved in the infection process. This situation is mainly due to the difficulty of conducting extensive genetic analyses in the targeted host cells and points to the need for developing genetic systems to model the infection process. Here, we describe a method (amenable to high-throughput analysis) that allows for the study of host factors involved in intracellular pathogen infection by using dsRNA-mediated gene expression knockdown [RNA interference (RNAi)] in Drosophila cell lines.