[Fever of unknown origin]

From a total of 4,123 hospitalized patients the criteria of fever of unknown origin were met by 81 (2%) who were divided with regard to the evoking cause into five groups: infection, tumors, rheumatic diseases, other diseases, diagnosis not established. The most frequent cause of fever was infection (29 patients, i. e. 35.8%), rheumatic diseases (16 patients, i. e. 19.7%), and the group of other diseases (14 patients, i. e. 17.3%). Tumors as the cause of fever held the fourth place (12 patients, i. e. 14.8%). In a small group of patients (10, i.e. 12.3%) the diagnosis was not established.