RNA silencing is a mechanism of genetic regulation that is mediated by short noncoding RNAs, or small RNAs (sRNAs). Regulatory interactions are established based on nucleotide sequence complementarity between the sRNAs and their targets. The development of new high-throughput sequencing technologies has accelerated the discovery of sRNAs in a variety of plants and animals. The use of these and other high-throughput technologies, such as microarrays, to measure RNA and protein concentrations of gene products potentially regulated by sRNAs has also been important for their functional characterisation. mRNAs targeted by sRNAs can produce new sRNAs or the protein encoded by the target mRNA can regulate other mRNAs. In either case the targeting sRNAs are parts of complex RNA networks therefore identifying and characterising sRNAs contribute to better understanding of RNA networks. In this chapter we will review RNA silencing, the different types of sRNAs that mediate it and the computational methods that have been developed to use high-throughput technologies in the study of sRNAs and their targets.