BACKGROUND AND OBJECTIVES: In 2009, pandemic H1N1 influenza A caused significant morbidity and mortality worldwide; however, available data on disease characteristics and outcome of hospitalized children is limited. DESIGN AND SETTING: A prospective cohort study of children who required hospitalization because of the influenza A (H1N1) infection at King Khalid University Hospital in Riyadh, Saudi Arabia, over 6 months (July December, 2009). PATIENTS AND METHODS: Data was collected using a predesigned form for all admitted pediatric cases (0-12 years) presenting with the influenza-like illness and who tested positive for the novel influenza (H1N1) using reverse transcriptase polymerase chain reaction assay. The clinical course and features associated with the severe disease among such children were described RESULTS: Out of 1103 children with the influenza-like illness, 375 (34%) were confirmed pediatric cases of influenza A (H1N1), of whom 50 (13.3%) required hospitalization. The median age was 3 years (range, 1 month-12 years). Fever was the most frequent symptom (94%) at admission, followed by cough (86%) and other symptoms including vomiting and diarrhea. The majority (70%) of children had at least one underlying medical condition, with bronchial asthma being the most common (40%). All cases were treated with oseltamivir. Five children (10%) were admitted to the ICU, 4 required mechanical ventilation, and 2 died (4%). CONCLUSIONS: The majority of children with 2009 H1N1 influenza A-associated hospitalization in this series had an uncomplicated course. Respiratory complications and ICU admissions were more frequent in those with underlying disease, especially asthma and neuromuscular diseases. Efforts need to be focused prior to each influenza season and special emphasis needs to be given to children by immunizing them with H1N1 influenza A vaccination to avoid severe disease and minimize complications.