The ubiquitous RNA-binding protein, Hfq, has been shown to be required for the fitness and virulence of an increasing number of bacterial pathogens. Mutants lacking Hfq are often sensitive to host defense mechanisms and highly attenuated in animal models, albeit there is considerable variation in both severity and extent of phenotypes. RNomics and deep sequencing (RNA-seq) approaches discovered the small RNA and mRNA targets of Hfq, and indicated that this protein might impact on the expression of up to 20% of all genes in some organisms, including genes of type 3 secretion systems. Hfq also facilitates post-transcriptional cross-talk between the core and variable genome regions of bacterial pathogens, and might help integrate horizontally acquired virulence genes into existing regulatory networks.