The prognosis of aggressive non-Hodgkin's lymphoma (NHL) has improved greatly during recent years with the use of combination chemotherapy. Planning the treatment must take into consideration the patient's age, performance status, histological subtype and disease extent and severity. Recently, a 4-part International Prognostic Index (IPI), based on 5 prognostic factors, has permitted the allocation of patients with NHL in 2 well defined prognostic groups: good prognosis (low and low-intermediate risk) and poor prognosis (intermediate-high and high risk). Conventional chemotherapy with CHOP (a chemotherapeutic regimen consisting of a combination of cyclophosphamide, doxorubicin, vincristine and prednisone) or other equivalent third-generation regimens may be considered the standard treatment for the good prognosis group. In the poor prognosis group the probability of long term survival is less than 40% with conventional chemotherapy. Therefore, an early intensification with high dose therapy following peripheral stem cell transplantation (PSCT) should be considered in the setting of randomised trials. Localised stage disease, defined as stages I-IE and II-IIE without adverse prognostic factors, has a very good prognosis with a long term survival exceeding 80% using brief conventional chemotherapy regimens plus involved field radiotherapy. Refractory or relapsing patients after the drugs of first choice are given who subsequently respond to salvage chemotherapy should be enrolled for a course of high dose consolidation chemotherapy followed by PSCT. Elderly patients without severe organ dysfunction can take advantage from specifically devised chemotherapy regimens, with a response rate similar to that of younger patients. However, despite major advances in the treatment of aggressive NHL, additional clinical trials are required to enable the clinician to define the best therapeutic programmes to treat patients with this disorder.