In order to evaluate the long-term results of allogeneic stem cell transplantation (ASCT) in B-cell chronic lymphocytic leukemia (CLL), we reviewed the outcome of 12 consecutive CLL patients, who underwent ASCT at the Mayo Clinic prior to July, 2004. Median age was 44 years (range 18-55) and median time from diagnosis to transplant 58.5 months. All patients had failed prior fludarabine-based chemotherapy and all but two patients had chemo-resistant refractory disease at time of transplant. A 'myeloablative' conditioning regimen was used in 11 patients and 'reduced intensity' in one. Bone marrow was the source of hematopoietic stem cells in 10 patients and peripheral blood in two. Donors were matched sibling in nine patients, unrelated in two and partial phenotypic match father in one. Grade II-IV acute and chronic graft versus host disease was documented in five and four patients, respectively. To date, six patients (50%) have died including four early deaths from infection. Complete remission (CR) was documented in eight patients (66.7%) post-transplant; six are currently alive whereas one died at 7 months from infection while still in CR and one relapsed 7 months post-transplant and died later. One CR patient relapsed after 4.5 years but was successfully re-transplanted and remains in second CR for 6.5+ years. Another patient recently relapsed after 10.5 years of CR. Duration of ASCT-induced CR in the remaining four patients was 6.5+, 8.5+, 9+ and 10+ years. All surviving patients displayed excellent performance status without ongoing chronic graft versus host disease. We conclude that ASCT is an effective salvage therapy for fludarabine-refractory CLL but late relapses can occur.