T-cell prolymphocytic leukemia (T-PLL) is a rare aggressive post-thymic malignancy with poor response to conventional treatment and short survival. It can readily be distinguished from other T-cell leukemias on the basis of the distinctive morphology, immunophenotype, and cytogenetics. Consistent chromosomal translocations involving the T-cell receptor gene and one of two protooncogenes (TCL-1 and MTCP-1) are seen in the majority of cases and are likely to be involved in the pathogenesis of the disorder. The CD52 antigen is expressed at high density on the malignant T-cells and therapy with alemtuzumab, a humanized IgG1 antibody that targets this antigen, has produced promising results. In relapsed/refractory patients overall and complete response rates have been seen in up to 76% and 60%, respectively. In previously untreated patients, complete remission rates of 100% have been reported. These responses are durable and translate into improved survival for responders. However, relapse is inevitable and strategies using both autologous and allogeneic stem cell transplantation are currently being explored. Additional clinical trials are investigating the use of alemtuzumabin combinations with chemotherapy, either concurrent or sequential. In the future we hope to have a betterunderstanding of how best to integrate these therapeutic approaches to further prolong survival for patients with T-PLL.