The bacterium Chlamydia trachomatis is an agent of sexually transmitted disease and represents the number one infectious agent reportable to the U.S. Centers for Disease Control. Primary infections do not elicit long-term protective immunity, re-infections are common, and C. trachomatis has a tremendous negative impact on human reproductive health world-wide. Chlamydia are spherical, obligate intracellular pathogens that parasitize human cells from within specialized vacuoles termed inclusions. The capacity to cause disease depends directly on the ability of chlamydiae to establish and maintain this protected intracellular niche. The Fields lab focuses on understanding how Chlamydia cause disease by elucidating the molecular mechanisms employed by chlamydiae to subvert and evade host defenses.