Abstract: Objective To explore the relationship of the fever of cause to be unknown (FOU) with the tuberculosis (TB). Methods To analyse of 258 cases of FOU from January 1980 to July 2000.Results 57.7% of FOU was diagnosed for TB,The clinical manifestations inTB group were different from that of the non-TB group significantly (P<0.005). Conclusion The important cause of the FOU is TB. The time of using anti-TB treatment in patients with suspect TB should be more than 2～2.5 months.

Key words: Tuberculosis, Fever