approximately 320 Army personnel, dependents, civilian employees, and guests at¬ tended a catered banquet in a private hall in San Antonio, Tex. Within a week nearly three-fourths of the diners were ill with what was later shown to be shigellosis (bacillary dysentery) caused by Shigella flexneri J^a. Shigellosis is an infection which frequently is not diagnosed because of the inadequacy or lack of laboratory facilities. The disease is endemic throughout a large part of the United States (1). In epidemic form shigel¬ losis has been less common than salmonellosis; explosive outbreaks have been reported infrequently. Usually protracted intra-institutional spread of the Shigella precedes the epidemic, which lasts weeks or months. Numerous rela¬ tively brief epidemics with high incidence also have been reported. Green and McLeod (2) described an outbreak of 400 cases in a small town of 10,000 population in England in 1942. Two hundred of these cases occurred within a 6-day period; the entire epidemic lasted 1 month. The medium of Dr.