Bacterial diarrheal diseases are a very important problem for human health, and many people, especially infants and children, die every year from diarrheal diseases, particularly in developing countries. Thus, in 1978 the World Health Organization initiated a Diarrhoeal Diseases Control Programme and is now working actively to control diarrheal diseases. The "International Symposium on Bacterial Diarrheal Diseases" which took place in Osaka from March 23rd to 25th, 1982, was organized by Osaka University with the support of the Ministry of Education, Science and Culture of the Japanese Government. The aim of this Symposium was to promote exchange of scientific information on bacterial diarrheal diseases, few years due since studies in this field have progressed rapidly during the last to work in many laboratories throughout the world. It seems appropriate that this Symposium was held in Osaka, since during the past century Japanese bacteriologists have made a number of important con tributions in the field of bacterial diarrheal diseases. Outstanding among these contributions are the recognition of Shigella as a causative agent of bacillary dysentery by Dr. Kiyoshi Shiga and the serotyping of Vibrio cholerae into the Ogawa, Inaba and Hikojima serotypes by Drs. Kabeshima and Nobechi. Moreover more recently, Dr. Tsunesaburo Fujino of Osaka University discovered Vibrio parahaemolyticus as the causative agent of an important diarrheal disease."