The field of infectious diseases covers many entities that can be considered true medical emergencies. Included are meningitis, brain abscess, spinal epidural abscess, epiglottitis, pneumonia, bacteremia, endocarditis, certain intraabdominal infections, gas gangrene, and necrotizing fasciitis. Because emergencies related to infectious agents are potentially the most readily reversible of all medical emergencies, it behooves us to diagnose them as rapidly and specifically as possible so that appropriate life-saving therapy may be begun expeditiously. This article reviews and summarizes the presentations of others in this issue and presents views on future prospects in the rapid diagnosis of infectious diseases.