Anaplastic large-cell lymphoma, T-/null-cell type (ALCL), is a rare disease that has only been well characterized for two decades. Despite this, the biology of ALCL is better understood than that of many other more common variants of lymphoma. This review focuses on the pathophysiology, clinical presentation, and therapy of ALCL, including stem cell transplantation. In particular, the text emphasizes how novel prognostic features and the evolving understanding of the biology of this disease will influence treatment selection and drug development.