Aim: To prospectively evaluate interferences between viruses of the upper respiratory tract in asymptomatic preschool children. Methods: Nasal-pharyngeal swabs from 233 preschool aged children were prospectively collected over four consecutive time periods, during one school year. The samples were tested using a RT-PCR DNA/RNA microarray system for nine respiratory viruses. Results: Respiratory syncytial virus (RSV) was a predictor of the presence of influenza virus (INFL) (OR: 9.12, CI: 1.52---54.75, p = 0.016), and similarly, INFL predicted the presence of RSV (OR: 4.01, CI: 1.14---14.16, p = 0.030). Also, rhinovirus (RV) was a predictor of adenovirus (ADV) presence (OR: 3.66, CI: 1.10---12.14, p = 0.034), and similarly, ADV predicted the presence of RV (OR: 4.05, CI: 1.02---16.05, p = 0.046). No other significant associations between viruses were observed. Conclusion: Our results indicate that respiratory viruses found in carrier stage in asymptomatic children may interact with other viruses and even facilitate their settling in the upper respiratory tract. The pathophysiological role of these interactions is not yet clear.