The first influenza pandemic of the 21st century started in April 2009 with an outbreak of swine origin influenza A(H1NI)2009 in Mexico and the United States. While generally a mild disease affecting mostly school-aged children and young adults, most attention went to severe cases of pneumonia in young previously healthy individuals or individuals belonging to a risk group. In this article we review the literature on the presentation and management of severe cases of influenza A(H1N1)2009 in the intensive care unit (ICU), and describe our own experience in a tertiary referral centre with ECMO facilities. Pregnant women and (bone marrow) transplant patients are two known risk groups for severe influenza described more thoroughly in this paper.These severely ill patients are characterized by respiratory failure, resulting often in the need of mechanical ventilation. As Oseltamivir resistance remains low up till now, early antiviral therapy with Oseltamivir is warranted in these cases. Despite pharmacological and ventilator management, refractory hypoxaemia is described frequently in these patients, with need for rescue therapies like nitric oxide inhalation, high frequency ventilation, and extracorporeal membrane oxygenation. The value of the use of corticosteroids is under discussion. Despite advances in management strategies, mortality and morbidity in these severe cases remains high. In the first influenza season after the pandemic, winter 2010/2011, influenza A(H1N1)2009 is the major influenza A strain in Europe, resulting in reports with increased mortality and morbidity compared to pre-pandemic seasonal influenza. "Continuing vigilance for severe influenza in patients not belonging to the classical influenza risk group might still be warranted for the upcoming influenza season".