This paper reviews our current knowledge about the evolution of virulence in pathogen-host systems, with an emphasis on the interface between the theoretical and experimental literature. After giving a methodically oriented  overview of the field, stressing restrictions and caveats, the paper attempts to summarize the main results on virulence evolution gleaned from the literature. From that perspective the authors identify what they see as gaps in our current knowledge that need to be filled to transform the study of virulence evolution and management into a mature science.