The global spread of novel influenza A (H1N1) led the World Health Organization to declare a pandemic on June 11, 2009. Our study aimed to describe the epidemiologic and clinical parameters of hospitalized patients during the pandemic. Fifty-one persons with suspected influenza A H1N1 were hospitalized. Thirty-two of them (14 male and 18 female) were positive for novel influenza A (H1N1) viral RNA by real time PCR in nasopharyngeal specimens. Of those who tested positive, 46.8% (15 patients) were aged between 25-49 years and only 9.3% (3) were over 65 years old. Nineteen of the 32 presented a co-morbidity. The mean duration of hospitalization was 6.5 days (range 3-19). An influenza complication was presented by 68.7% of patients (all of them older than 65 years), which in most cases was pulmonary disease (18 bronchopneumonia, 2 interstitial pneumonia). Four patients required mechanical ventilation in Intensive Therapy Care. One patient died of a concomitant myopericarditis. Of the patients with influenza complications, 60% presented co-morbidity conditions. Neurologic complication (encephalitis) occurred in two young women; prognosis was good and without neurologic sequelae. In conclusion, our data do not show a correlation between gender and risk of hospitalization or influenza complication. The presence of co-morbidity does not increase the risk of pulmonary complication, which is more frequent among young adults.