We evaluate whether molecular monitoring of minimal residual disease (MRD) using TCR delta (TCRD), TCR gamma (TCRG), and immunoglobulin H (IgH) gene rearrangements in the bone marrow (BM) is correlated with clinical events in ALL patients. The 14 patients enrolled in this study included 6 males and 8 females with a median age of 53 years (range, 25-79 years), and the median duration of follow-up was 417 days (range, 57-617 days). The median WBC count was 11.3 x 10(9)/L at diagnosis. All patients had L2 type ALL. Eleven patients had a monoclonal pattern of IgH (7), TCRD (3) and TCRG (1), and 3 patients had two clonal patterns. Eleven of the 14 patients achieved the first complete remission (CR) after the first induction chemotherapy. We analyzed 9 of 11 CR patients who could be examined immediately after induction chemotherapy (including re-induction therapy). Event-free survival (EFS, 0%) and disease-free survival (DFS, 0%) at 1 year in CR patients with MRD level >or=10(-3) (n = 3) were significantly lower than those in CR patients with MRD level <10(-3) (n = 6) (log-rank test, P = 0.013, 0.013). A lower MRD in BM value after induction chemotherapy was associated significantly with longer survival in the log-rank test. Our data provide evidence that molecular MRD status of BM is a strong predictor of outcome in adult ALL.