Acute respiratory tract infections (ARTIs) are associated with significant morbidity and mortality worldwide, especially in developing countries. Children under the age of 5 years old are mostly affected. Both viral and bacterial causes are implicated, but viral etiologies are more difficult to diagnose. Viral infections can occur either single or mixed, but the significance and association of polyviral agents with the severity of cases are poorly understood. More studies are critical for understanding this role, improving diagnosis and treatment.Objective: To identify the rule of five chosen viral pathogens in ARTIs in children below 5 years old and the association of polyviral etiology with the severity of the disease.Methods: Nasopharyngeal swabs were taken from 120 children who had symptoms and signs of ARTIs, attending the outpatient clinic and admitted in pediatric department or pediatric intensive care unit, Banha university hospital. All children were subjected to full history taking, analysis by multiplex PCR for five viruses (Rhinovirus, Respiratory syncytial virus, Human metapneumovirus, Adenovirus, and Human boca virus).Results: 54 viruses were identified by multiplex PCR from 41 children (34.2%), 75.6% of them had a single viral infection, (17% and 7.4%) were co-infected with two and three viruses respectively. Positive cases were mostly of children admitted in pediatric ward and the majority were infants. URTIs was the most common presentation followed by bronchiolitis then bronchopneumonia. HRV was the most frequently detected as a single and mixed infection (35.2%) followed by RSV (22.2%). Non-significant correlation was found between mixed infection and the severity of infection. Conclusion:HRV is the most frequently recognized viral pathogen either as single or mixed in children below 5 years old in our patient group. Mixed infection has no correlation with disease severity. And using Multiplex PCR is an ideal tool for investigating mixed infection.