Humans display a remarkably diverse susceptibility to infection, the foundation of which lies in our genetic variation and ability to respond to selective pressures applied by various infectious agents. The evolution of our complex and multiplayer immune system underlines the dominance of the human host following a microbial infection. However, given the nature of obligate intracellular pathogens, their complete reliance on host gene expression machinery has led to the evolution of complex interplays between the two, such that pathogens actively and strategically maneuver their way through the host terrain. Our traditional view of this terrain as being comprised of protein-coding genes, translation intermediates (mRNAs) and protein counterparts is far too simplistic, particularly in the context of infection. The discovery of the RNA interference (RNAi) pathway has greatly enhanced our understanding of the host terrain. Small noncoding RNAs (ncRNAs) termed microRNAs (miRNAs) were shown to be key regulators of gene expression that function within the RNAi pathway to post-transcriptionally modulate mRNA stability and subsequent translation . Indeed, it is now understood that miRNAs are able to rapidly, and with exquisite specificity, modulate gene expression in response to numerous environmental cues in a highly coordinated, complex and tissue-specific manner. Given the reliance of intracellular pathogens on host gene expression machinery, the RNAi pathway, and specifically miRNAs, are now understood to lie at the nexus of the host-pathogen interplay. The focus of this chapter will be on the characteristics and roles of these small noncoding RNAs in host-pathogens interactions.