Acute respiratory infection (ARI) is the leading cause of mortality and morbidity among children under 5 years. The study was conducted to describe some factors and to identify ARI rate among children under 5 years in Bavi- Hanoi, 2010. The results showed that, the rate of ARI in one month was 72 percent among children under 5 years. Girls had more ARI than boys (75 percent vs. 71 percent, p 0.05). The rate of ARI was highest among children from 12-60 months (76.8 percent). children belong to household with poor economic status, farmer mother suffered from ARI higher than other (p 0.05). In conclusions, continuous health education about ARI among children under 5 years is important for reducing ARI rate. especially in poor group.