We describe the epidemiology, clinical features, radiological findings, therapy and course for 15 patients hospitalized at the Infectious Diseases UOC of Gravina Hospital Caltagirone for a serious respiratory condition with verified infection A (H1N1) from 9 November to 22 December 2009. We retrospectively reviewed medical records, laboratory and instrumental tests performed on hospitalized patients. All patients had significant respiratory impairment: nine had co-morbidities and risk factors such as obesity, pregnancy, immunosuppressant conditions and muscular dystrophy. Symptoms were similar to those of seasonal influenza; radiological investigation of the chest (RX and CT) presents lung involvement in 80% of patients and changes in the bio-humoral indices. Development into acute respiratory distress syndrome (ARDS) was observed in six patients: three were ventilated with a Venturi mask, three were treated in intensive care and two patients used extracorporeal membrane oxygenation (ECMO). Two died. All patients received antiviral and symptomatic therapy for 5-21 days. A(H1N1) virus infection led to a mild to moderate flu syndrome, which was often cured by symptomatic treatment; some patients required hospitalization for viral pneumonia, mixed pneumonia or ARDS. In previous flu epidemics there was no development into ARDS (40% in our series).