Malignant lymphomas are increasing in frequency for unknown reasons. We know today that they constitute a big family of tumours of lymphoproliferative origin, which can be very different one from the other in terms of morphology, biology, and clinical behaviour. Some of them need very specific treatments and it is therefore important that a clear diagnosis is obtained and that the treatment is administered by specialised doctors. Although the new WHO classification has abolished the concepts of low-grade and high-grade lymphomas, it remains true that some lymphomas exhibit indolent behaviour and cannot be cured, while other aggressive lymphomas can be cured by modern therapy. The cornerstone of treatment remains chemotherapy and, to a minor extent, radiotherapy. New treatment modalities such as the use of monoclonal antibodies, high-dose therapy or allogenic transplantation have improved the treatment results in the last decade. In this article we offer a summary of the most important concepts which are of interest for practising physicians.