Polo-like kinases (Plks) are a highly conserved family of kinases found in flies, yeast and vertebrates. Plks derive their name from homology to the gene product of polo, a protein kinase first identified in Drosophila. Three polo-like kinases have been identified in vertebrates: Plk1, Plk2 and Plk3. Studies on Plk1 have revealed a great deal of information on its multiple functions, however Plk2 and Plk3 functions have not been fully explored. In this perspective we discuss recent work on Plk3 expression, function and localization in the context of previous reports on Plk3 and in terms of its relationship to Plk1.