The share of various etiologic forms of acute intestinal infections, diagnosed by bacteriologic methods, is presented. The share of gastroenterocolitis induced by opportunistic microflora makes up 35.6%, that of dysentery 25.6%, salmonellosis 18.5%; mixed infection (dysentery + salmonellosis) is diagnosed in 7% of cases with acute intestinal infections. The principal representative of opportunistic microflora isolated from patients with acute intestinal infections is the Klebsiella genus (40.6%), whereas in the reference group Citrobacter, Morganella, and Klebsiella detection rates are approximately the same (27.0-18.3%). Opportunistic microorganisms in titers under 10(6) are isolated from normal subjects 5 times more frequently than from the patients, this indicating the diagnostic value of this level of feces contamination with opportunistic microflora.