This book summarizes the progress in studies of tuberculosis host-pathogen interactions from several perspectives: molecular microbiology, immunology, animal models, clinical studies, epidemiology, and drug discovery. Tuberculosis (TB) remains a severe global public health problem. Complex interactions between environmental, microbial and host factors lead to clinically relevant infections.  Studies on bacterial virulence, host-genetic, and immunological factors contributing to the susceptibility to TB provide an ever-growing foundation of knowledge that is critical to finding new interventions.  Studies of immune mechanisms against M. tuberculosis infection have identified immunological markers associated with specific phenotypes in the host, providing insight into how they may be used to augment current treatment strategies. Recent advances in diagnosis, therapeutics and vaccines, as well as basic-research oriented studies have shed light on the development of new directions for prevention, treatment and control of TB. Improved understanding of the interplay between the bacterium and host is a key component of reducing incidence worldwide.