The aim of the research: identification of etiological structure of acute diarrheas and hemorrhagic colitis in Georgia, manifestation of clinical peculiarities and predictors of hemorrhagic colitis complicated by HUS ( Hemolytic-Uremic syndrome). In 2011-2013 we studied 274 hospitalized patients at the Center of Infectious Diseases, AIDS and Clinical Immunology (160 hemorrhagic colitis and 114 non-bloody diarrhea). Causative agents of hemorrhagic colitis (160 patients) were determined in 110 (69%) cases; etiology of the non-bloody diarrhea (114 patients) was established in 46 (40%) cases. Enteronterohaemorrhagic E. coli (EHEC) strains are major causes of hemorrhagic colitis. For the confirmation of STEC infection by the bacteriological investigation some significant additional methods were used: serologic examination of feces on shiga- toxin molecular markers by ImmunoCard STAT and PCR methods. Thus, these above mentioned investigations contribute to diagnosis STEC infection at the early stage of the disease. Based on our findings we were able to reveal predictors of complications of hemorrhagic colitis by HUS. They include: Delayed hospitalization, rural residents, premorbid background, onset of the disease with low-grade fever accompanied with abdominal cramps, manifestation of bloody diarrhea on the 2-3-rd days of the disease, frequent bowl movement (>20 times a day), development of oliguria and edema on the following days, leucocytosis in hemogram, elevation of LDH, creatinine and urea, hypoalbuminemia and development of ascites.