Purpose of ReviewMarek’s disease virus (MDV) is a highly oncogenic alphaherpesvirus that causes various clinical symptomsincluding fatal lymphomas in chickens. The virus encodes several MDV-specific genes that play a major role in viral pathogen-esis. This review will focus on the recent advances in our understanding of how these viral factors contribute to pathogenesis andtumor formation.Recent FindingsSeveral viral factors involved in MDV pathogenesis have been identified including the major oncoprotein Meq,the viral chemokine vIL-8, MDV-encoded microRNAs, RLORF4, RLORF5a, pp14, pp38, a virus-encoded telomerase RNA(vTR), and viral telomeric repeats (TMRs). Our current knowledge of the role of these viral factors in MDV pathogenesis hasimmensely increased over the last few years; however, more work needs to be done to completely understand the mechanisms formost of them.SummaryMDV pathogenesis and tumor formation is a complex process. Deciphering the mechanisms of viral factors involvedin MDV pathogenesis and lymphomagenesis will not only improve our understanding of this neoplastic disease but will alsoprovide new strategies for vaccine development against this deadly pathogen.