A symposium seems an appropriate vehicle to review recent, as well as new, data on important topics. It is therefore our goal to present a symposium on selected topics of importance every three years. Some topics will be updated and new topics will be presented. A vast amount of information has been accumulated over the past ten years on the significance of anaerobic bacteria in infectious diseases. This symposium was organized to discuss laboratory aspects, normal flora, pathogenicity, serology, and the patients' immune re sponse to anaerobic infection. Important imformation on the patients' immune response and serology of anaerobes which has accumulated over the last few years made these topics an important part of the sympo sium. Development of serological diagnostic tests undoubtedly will provide quicker and less expensive identification of certain anaerobic species in the future. Utilization of the patients' immune response to anaerobic septicemia has the potential of providing a diagnosis of the causative agent within 24 hours after onset of symptoms. The development of such diagnostic methods and the use of these methods in the clinical laboratory in the future would provide rapid diag nostic information to the clinician on these life-threatening infec tions. Campylobacter was included in the symposium to emphasize the important role of this organism in human acute gastroenteritis. The pathogenesis of Campylobacter in gastroenteritis has been recognized in certain European countries since 1972, although we have recognized the importance of Campylobacter gastroenteritis in the United States only within the past two years."