Fever characteristics were analyzed in 597 cases of tuberculosis diagnosed by positive culture for mycobacteria tuberculosis admitted to Chang Gung Memorial Hospital between March 1984 and February 1986. Among them, fever was noted in 356 cases (60.0%). Several factors were predisposing to the absence of fever: having a past history of tuberculosis (p less than or equal to 0.01), having a limited lung lesion (p less than 0.05), having an infection with isoniazide (INH) resistant strain (p less than 0.05). Fever typically developed in the late afternoon or evening in 66% of the cases, and this typical fever was significantly more common in patients less 60 years of age (p less than 0.05). The fever was low grade (less than 38.5 degrees C) in 59% of the cases. Among the 137 cases whose fever courses were completely monitored in the hospital, there were 30 cases (22%) whose fever subsided within 3 days after the start of antituberculous chemotherapy, 102 cases (74%) within 1 week and 128 cases (93%) within 2 weeks. Fever resolved within 4 weeks in all but one patient. There was no clinical factor predisposing to the delay of time for the fever to resolve including sex, age, immunocompromised condition, having a past history of tuberculosis, the infectious site(s) of tuberculosis, the extent of pulmonary involvement, the presence of cavitation in pulmonary involvement, and infection with resistant strains.