Twenty patients with poor prognosis B-cell chronic lymphocytic leukemia (B-CLL) underwent uniform high-dose chemoradiotherapy followed by rescue with multiple monoclonal antibody-purged autologous bone marrow (BM) (12 patients) or T-cell-depleted allogeneic BM from HLA-identical siblings (8 patients) in a pilot study to assess the feasibility of BM transplantation (BMT) in this disease. All had poor prognosis disease by either staging, BM pattern, tumor doubling time criteria, or cytogenetics. All patients achieved remission criteria (defined as < or = 2 adenopathy, absence of splenomegaly, < or = 20% of the intertrabecular space involved on BM biopsy) before BMT. Despite the use of fludarabine, a median of three treatment regimens were required to achieve BMT eligibility. After BMT, all patients achieved complete hematologic engraftment. Toxicities were not significantly different between autologous versus allogeneic BMT. Two toxic deaths were observed. Of 19 evaluable patients, 17 clinical complete clinical remissions (89%) were observed, with 2 patients (1 allogeneic and 1 autologous) exhibiting persistent BM disease. Complete clinical remissions were documented at the phenotypic and molecular level for the majority of patients in whom dual fluorescence for CD5 and CD20 (15 of 15; 100%) and Ig gene rearrangements (11 of 14; 79%) were performed. Although long-term follow-up is needed to assess any potential impact on the disease-free and overall survival of these patients, this study shows the feasibility of using high-dose chemoradiotherapy and BMT in patients with poor prognosis B-CLL.