Aim. To assess the clinical efficacy and safety of three antiviral therapy regimens (riamilovir, umifenovir, and enisamium iodide) in the treatment of moderate acute respiratory viral infections (ARVIs) when initiated at a later stage of the acute disease period. Material and methods. The study included 200 male participants aged 18–27 years, randomly assigned into four equal groups. Three groups received one of the antiviral drugs in standard doses, while the fourth served as a control group and received only pathogenetic therapy. The following outcomes were evaluated: severity and duration of ARVI clinical symptoms, length of hospitalization, incidence of complications, and the presence of viral pathogens (PCR testing on days 1 and 6). Quantitative variables are presented as median (Me) and interquar-tile range (Q1; Q3) or mean (M) and standard deviation (SD). Normality was assessed using the Shapiro–Wilk test. Statistical analysis included non-parametric methods and the c2 test. The Kruskal–Wallis test was used to compare indicators between four independent groups. In cases of statistically significant differences (p