The recent sequencing of mycoplasma genomes has marked a turning point in the molecular genetic analysis of these microorganisms. Transcriptome and proteome analyses promise to provide the first definition of the total protein complement of a cell. The mycoplasma group includes the smallest known self-replicating organisms carrying the smallest number of genes. No wonder, therefore, that mycoplasmas have a special appeal to those interested in deciphering the minimal set of genes essential for life. Mycoplasma genomics facilitated better understanding of mycoplasma pathogenesis. Most impressive are the findings concerning the interaction of mycoplasmas with the immune system, macrophage activation, cytokine induction, mycoplasma cell components acting as superantigens, and autoimmune manifestations. The molecular definition of mycoplasmal adhesins responsible for mycoplasma attachment to host cells and evasion of the host immune system by antigenic variation of mycoplasmal surface components are other `hot' subjects of research. Demonstration of the ability of mycoplasmas to enter host cells, cause fusogenic, apoptotic and oncogenic effects, as well as the possible association of mycoplasmas with arthritis, had their share in intensifying research on mycoplasma pathogenesis, bringing more researchers into the circle of those interested in this group of organisms. The present book is a comprehensive, up-to-date, multi-authored treatise.