Rötfeber (decay fever) was a category of fever illnesses mentioned frequently in Swedish district physicians’ yearly reports in the 19th century, but despite its frequency there is no real agreement on what rötfeber entails. In this thesis, I wanted to come to an understanding of how rötfeber could be defined and which people received the diagnosis. With the help of the physicians’ reports I examined how they discussed rötfeber and compared it to other diseases: Some physicians described it similarly to a common cold, while others meant it commonly resulted in death or acted as the worsening of a patient’s already terminal disease, such as cholera or typhus, or was synonymous with it. A lot of descriptions of rötfeber also coincided with descriptions of medical traditions based on one’s environment being the cause of disease, with polluted air or dirt often being named the transmitter of disease. While reading the reports, I noticed a pattern of rötfeber often being discussed in connection with a district’s poorer population. The physicians described how their way of living with unhealthy air and bad circulation, unhealthy foods, and lack of hygiene made them ill with rötfeber. The disease became a portrait of a poor person, and a rötfeber diagnosis could be used to further stigmatize already vulnerable people and survey them. Poor people were thus the people most often receiving the diagnosis and rötfeber itself was described to occur due to unhealthy living, which also defined the disease.