Patients with a non-Hodgkin lymphoma of low-grade malignancy have been considered incurable for decades. Several conventional therapies have resulted in an improved disease-free survival but not in a prolonged overall survival. Intensified treatment of relapsed patients with myeloablative conditioning followed by autologous or allogeneic stem cell transplantation (SCT) is being applied more and more. In both forms of SCT the anti-tumour effect of the high-dose chemo- (and radio-) therapy is used; allogeneic SCT has an additional so-called graft-versus-lymphoma effect. Thus allogeneic SCT appears to be a promising and potentially curative treatment for this patient group, despite complications like graft-versus-host disease and higher treatment-related mortality. Early in the course of a low-grade NHL, especially at first relapse, an allogeneic SCT should at least be considered for a patient having an HLA-compatible stem cell donor.