The problem of antibiotic-associated conditions is one of the most actual problems of clinical practice. The antibiotic-associated diarrhea is a multidisciplinary problem. Investigations of the small intestine microecological status and assessment of microflora at the patients receiving antibiotics testifies to dysbiosis existence. In article results of open-label investigation of a multispecies probiotic RioFlora Balance using for antibiotic-associated diarrhea prophylaxis in patients used antibacterial therapy are presented.