Influenza pandemics show a history of recurrence. In the 20th century, three influenza pandemics occurred. The swine flu is now a reality, the first pandemic of the 21st century. Among the influenza pandemics of the 20th century, the Spanish flu was the most lethal, and terrifying due to recurring waves and the fact that the lethality was highest among young and healthy adults. Information about historical pandemics is of great value, to be able to prepare for future pandemics. In this study we focus on two areas: An investigation of historical autopsy data from Ullevål hospital in Oslo from the period of the Spanish flu, as well as an investigation of available literature on several aspects of influenza pandemics. The data from Ullevål hospital verifies the results from earlier studies of the Spanish flu in Norway, regarding age distribution and the pattern of recurring waves. The intention of the literature investigation is both to compare the data from the Ullevål hospital with other studies of the Spanish flu, as well as to discuss the available information from historical influenza pandemics in general. We are focusing on lethality, on cause of death, on the properties of the influenza virus in general, on viral dynamics, on modeling pandemic spread, on intervention strategies etc. The conclusion of the literature investigation is that available information is not sufficient to explain all properties of and differences between historical pandemics. All data about historical pandemics as well as the ongoing swine flu pandemic, could be valuable.