MicroRNAs are a recently discovered class of small noncoding functional RNAs. 
These molecules mediate post-transcriptional regulation of gene expression in a 
sequence specific manner. MicroRNAs are now known to be key players in a variety 
of biological processes and have been shown to be deregulated in a number of 
cancers. The discovery of viral encoded microRNAs, especially from a family of 
oncogenic viruses, has attracted immense attention towards the possibility of 
microRNAs as critical modulators of viral oncogenesis. The host-virus crosstalk 
mediated by microRNAs, messenger RNAs and proteins, is complex and involves the 
different cellular regulatory layers. In this commentary, we describe models of 
microRNA mediated viral oncogenesis.