BACKGROUND: Abnormalities of the peripheral blood are frequent and varied in patients with miliary tuberculosis. Anemia,leukopenia, thrombocytopenia, pancytopenia, monocytosis, basophilia, eosinophilia and leukemoid reactions have been reported. These abnormalities are more frequent in patients with positive bone marrow study. In this report, we evaluated clinical, hematological and immunological features in patients with miliary tuberculosis in order to know whether difference is existed between "bone marrow biopsy positive group(pathologically proven to miliary tuberculosis)" and "negative group". METHOD: Clinical evaluation, serum ADA, sIL-2R, and T-lymphocyte subsets were measured in 40 patients with miliary tuberculosis who received bone marrow biopsy. RESULTS: 1) The average age of patients was 39 year-old. There were 23 male and 17 female patients. Associated extrapulmonary tuberculosis are 9 CNS tuberculosis, 6 joint tuberculosis, and 2 tuberculous pleurisy. 2) Sixteen of the 40 patients were positive bone marrow biopsy(60%). 3) Sixteen of the 40 patients(60%) had anemia(ll positive patients: 13 negative patients). Leukopenia occurred in 12 per cent(4:l). Thrombocytopenia was noted in 10%(3:1). 4) The mean value of serum ADA was 83 U/L(90 U/L: 70.6 U/L, p=0.23). 5) The mean activity of Soluble IL-2 receptor was 4,643 pmol/L(6840+/-7446 pmol/L: 1,897 +/- 1,663 pmol/L, p=0.06). 6) In the T lymphocyte subsets, the percent of T-lymphocytes was 64%(62%:73%, p=0.2). In some patients(9), T4 and T8 ratio in BAL fluid(1.97+/-1.2) was higher than that in the peripheral blood(1.16+/-0.5). CONCLUSION: Bone marrow examination are diagnostic in 60% of cases of miliary tuberculosis. Percents of the total T lymphocyte and helper T cell in BAL are more elevated than in peripheral blood. There was no significant difference in peripheral blood abnormalities and marker of T lymphocyte activation between the bone marrow biopsy positive and negative group.