We describe the results from a nation-wide surveillance study on severe paediatric seasonal influenza cases in Germany during three pre-pandemic influenza seasons between 2005 and 2008. A total of 20 laboratory-confirmed influenza-associated PICU cases (14 influenza type A, 5 type B, 1 type unknown), including two fatalities, were reported. This number was surprisingly low and corresponded to an estimated annual incidence for PICUadmitted children with seasonal influenza of 0.1/100,000 children < 5 years of age. In contrast, for the same age group incidences of PICU admissions associated with seasonal influenza were 4/100,000 in USA and 1-13/100,000 in South Australia [5, 7] . Apart from country-specific differences in access to health care as well as in criteria for ICU hospitalisation, the lower incidence found in our study may also be due to the weak to moderate influenza activity during the observation period in Germany [11] . Another important explanation is possible under-diagnosis of influenza in the hospitals, as not all physicians perform influenza testing of children admitted with severe acute respiratory infection. Low participation in the voluntary reporting system due to frequent changes of the medical staff in the PICUs is a further possible reason. Hence, the low reported incidence for PICU-admitted influenza cases in this study may underestimate the true incidence of severe paediatric influenza cases in Germany. With regard to fatal paediatric cases it should be noted that our study was not designed to capture influenza-associated fatalities that occurred outside PICUs, e.g. at home or during emergency treatment. For comparison, the national mortality register reported a total of 25 influenza-associated (ICD-10 code J10) deaths in children < 15 years of age during the years 2006 to 2008.