Abstract: Objective To determine the epidemiological characteristics of influenza A (H1N1) in Mianyang. Methods Descriptive epidemiological approaches were employed to analyze the data on influenza A (H1N1) collected from the China Information System for Disease Control and results of on-spot investigations. Results A total of 407 influenza A/(H1N1) cases were confirmed in Mianyang in 2009. Among them, there were 393 confirmed cases through laboratory test, 14 suspected, 20 severe, 6 critically severe cases, and 1 death. Influenza A (H1N1) outbreaks were present in the 9 counties under Mianyang. The top-three highest incidence rates were from Fucheng (60.20%), Santai (18.67%) and Anxian (6.88%). The incidence peaked from September to October. The average age of confirmed patients was 16.6 years, and the male to female ratio was 1.51 ∶ 1. Conclusion In view of the serious epidemic of influenza A (H1N1) in Mianyang, it is important to strengthen the surveillance of influenza-like illness and the diagnosis and management of severe cases, and to promote vaccine inoculation for vulnerable population.