We are at the beginning of the third decade of studies at the molecular level on the pathogenesis of Listeria monocytogenes and the response of the host to its infections. It is a good time to survey the wealth of information that these studies have revealed and to think about perspectives for a more complete understanding of this important pathogen. During the past 20 years, L. mono- togenes has emerged from relative obscurity to being one of the most intensely studied bacterial pathogens. In the opening chapter, Daniel A. Portnoy provides a personal and historical account of the development...