Even in the US, infectious diseases are the third most common cause of death, despite the widespread availability of antibiotics, vaccines, and advanced hygienic standards. The identification of new pathogens, the re-emergence of old pathogens, and the increasing incidence of antibiotic resistance reflect the globalization of humanity and microbes. As illustrated by the recent anthrax, SARS, and monkeypox outbreaks, new as well as old pathogens can be rapidly moved great distances and establish footholds in new niches. Strategies for the prevention, treatment, and control of infectious diseases will require fundamental bench research that takes advantages of rapid advances in genomics, proteomics, cell biology, and immunology to develop new diagnostics, therapeutics, and vaccines. The study of microbial pathogenesis is a rapidly advancing area of research, with unprecedented opportunity to influence health worldwide. Over the past 5 years, UCSF has created a strong training environment and established an outstanding program in Infectious Disease and Host Defense. There are 26 faculty already associated with the program and several new hires planned; space and resources to recruit 2-3 more faculty have been allocated; a course, journal club and research talks are now offered, and a yearly symposium established. This new T32 grant application describes the new program at UCSF in Microbial Pathogenesis and Host Defense that will train the next generation of scientists who can combat disease through advances in basic and translational research. [unreadable] [unreadable]