The transplantation of stem cells from a healthy donor (allogeneic) offers the chance of cure for patients with an aggressive form of chronic lymphocytic leukemia (CLL), irrespective of genetic prognostic factors and the prior course of the disease. The German CLL Study Group proved this in a multicentric clinical phase II study led by Professor Dr. Peter Dreger, senior consultant and head of the division of stem cell transplantation at the Department of Internal Medicine V at Heidelberg University Hospital.