Since its first recognition, the 2009 pandemic influenza A (H1N1) virus rapidly spread worldwide. We observed the clinical characteristics of 167 hospitalized patients who were confirmed by testing pharyngeal or nasopharyngeal swabs with the use of a real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assay. The mean age of the 167 hospitalized patients was 4.1 years, and 58.7% were male. The most common symptoms and signs were fever (91.6%), cough (82.6%), pharyngeal congestion (95.2%), and swollen tonsils (34.1%). The major complications were bronchitis (19.2%), bronchial pneumonia (10.8%), neutropenia (49.7%), and leukopenia (38.9%). The duration of hospitalization, fever and the course of disease in the patients who were treated with oseltamivir were shorter than in those who were treated with ribavirin. All of the patients fully recuperated from the 2009 epidemic influenza A (H1N1) infection with one exception.