During the first wave of the A/H1N1v influenza pandemic in Switzerland we followed the disease course of 15 patients with A/H1N1v-associated pneumonia. Oseltamivir treatment was initiated on day seven (median) after onset of symptoms. Of the patients studied 14 had to be hospitalised, with a median hospital stay of 8-9 days; 6 were admitted to intensive care, of whom 3 required intubation. According to WHO recommendations, oseltamivir should be started as early as possible, both in patients with risk factors for severe disease and in any patient presenting with symptoms of progressive disease. If treated early according to these guidelines, half of our patients might not have developed pneumonia at all. In the remaining patients without preexisting risk factors, the clinical course of pneumonia might have been milder. It is questionable whether the delayed oseltamivir treatment still influenced the clinical outcome, but no patient died; the two patients who were discharged with new home oxygen therapy apparatus had presented massive preexisting morbidities.