BACH2, a B-cell-specific transcription repressor, is abundantly expressed in lymphocytes of B-cell lineage as well as B-cell lymphoma cell lines. BACH2 possesses an inhibitory effect on proliferation of Raji cell lines derived from Burkitt's lymphoma. In this study, the prognostic significance of BACH2 expression was examined in diffuse large B-cell lymphoma (DLBCL). BACH2 expression was immunohistochemically examined on the paraffin-embedded sections obtained by biopsy from 108 patients (62 males and 46 females; age range, 23 to 85 years) with DLBCL. Staining intensity in the cytoplasm of the tumor cells was categorized as equal to or stronger (level 1) or weaker (level 2) than that in the endothelial cells in the same specimens. Level 1 and 2 expression of BACH2 was found in 32.4% and 67.6% of patients, respectively. Patients with level 1 expression showed significantly better disease-free and overall survival rate than those with level 2 expression (both P < .05). Multivariate analysis revealed BACH2 expression level together with performance status, elevated serum level of lactate dehydrogenase, and treatment response to be independent factors for prognosis of the patients. BACH2 expression level is a useful marker to predict disease-free and overall survival of patients with DLBCL.