Background: Over the past few years several patients with severe pneumococcal sepsis were admitted to the medical intensive care unit (ICU) presenting a more serious clinical picture than expected. We therefore wanted to study patients with severe pneumococcal sepsis thru their course of disease from admission throughout the hospitalization.Material and method: A combined retrospective and prospective study of patients with pneumococcal sepsis admitted to the ICU at Ullevål hospital. The inclusion criteria were growth of Streptococcus pneumoniae in blood culture and respiratory failure treated with ventilator. Results and discussion: We found that 16 patients that were admitted from 01.01.06 to 01.08.11 fulfilled the inclusion criteria. 38% of the patients died, 19% survived with sequlae and 44% returned to their habitual state. The age varied from 22 – 73 years and 50% didn’t have any obvious risk factors. For 88 % it took less than 24 hours from the time they needed medical help until they were intubated. At the time of hospitalization 93% had sepsis (by SIRS criteria). All patients had multiorgan failure. Surprisingly, 25 % of the patients needed amputation of one or more limbs. Conclusion: Pneumococcal sepsis can occur in young people without obvious risk factors, can have a very rapid disease progression, almost 40% mortality and 25% of the patients needed amputation of one or more limbs. The results indicated a more serious presentation and course than previously described and this disease now seems to be the most challenging septicemia in medical patients.