Purpose: To study the clinical aspects of influenza and acute respiratory viral infection (ARVI) in routine clinical practice, with efficacy and safety of the antiviral therapy evaluation. Subjects and methods: In the large multicenter prospective observational study were enrolled 18,946 patients aged 18 to 93 years with previously determined diagnosis of influenza or ARVI from 262 outpatient sites in Russia, Armenia, Moldova and Georgia. According to study design, 3 visits were evaluated. On each visit the detailed medical examination, determination of individual symptoms’ severity and course of disease were made. The dynamic evaluation of prescribed in routine clinical practice therapy of influenza and ARVI and cases of disease exacerbations with antibiotics concomitant therapy were assessed. Results: For the first time in outpatient practice on a large population of adult patients the objective data were obtained and analyzed. This data relating to the timing of access to medical care of patients with influenza and ARVI depending on the age and the disease severity, dynamics of clinical picture of the disease, their outcomes, timing recovery, as well as ongoing drug therapy of ARVI and influenza, allowed to identify patterns of development and course of these diseases. The effectiveness and safety of antiviral drug Kagocel for treatment of ARVI and influenza was shown. This is reflected in the improvement of the clinical picture of the disease; reducing the number of patients with exacerbations, requiring the prescription of systemic antibiotics up to 1.5 times; the acceleration of regression of symptoms and recovery periods. Conclusion: This study allows increase the level of objective assessment of the beginning and course of influenza and other ARVIs in outpatient practice, to predict their course and outcome, and to improve the treatment