Tuberculosis (TB) may produce abnormalities in the peripheral blood, including anemia. However, the evolution of TB-associated anemia with short-term combination anti-TB chemotherapy has not been well elucidated. The aim of this study was to characterize TB-associated anemia by clarifying its prevalence, characteristics, and evolution, through involving large numbers of patients with TB. The medical records of adult patients with TB diagnosed between June 2000 and May 2001 were reviewed. Among 880 patients with TB, 281 (31.9%) had anemia on diagnosis of TB, however, the hemoglobin concentration was less than 10 g/dL in only 45 patients (5.0%). Anemia was more frequently associated with the female and old age. Good treatment response, young age (< or =65 yr-old) and initial high hemoglobin were the predictive factor for resolution of anemia. In 202 patients with anemia (71.9%), anemia was normocytic and normochromic. During or after anti-TB treatment, anemia was resolved in 175 (64.6%) out of 271 patients without iron intake. The mean duration of resolution from the initiation of anti-TB treatment was 118.8+/-113.2 days. In conclusion, anemia is a common hematological abnormality in patients with TB and close observation is sufficient for patients with TB-associated anemia, because TB-associated anemia is usually mild and resolves with anti-TB treatment.