The majority of the patients with non-Hodgkin's lymphoma present with extensive disease at diagnosis. Extranodal is the most common primary site and Non-lymphoblastic histology is the most common histological subtype in pediatric lymphomas of which diffuse histiocytic is certainly the most common of the group, second only to diffuse lymphoblastic histology. Certain histological subtypes are associated with certain primary sites. The LSA2-L2 has been shown in this group to be as effective for lymphoblastic lymphoma as for non-lymphoblastic lymphomas, a slightly lower disease-free survival is due to the fact that, in this group, certain factors such as initial central nervous system involvement, initial bone marrow involvement, and high serum lactic dehydrogenase levels seem to play an important role in prognosis. The comparison of the disease-free survival for the two major subgroups, lymphoblastic and non-lymphoblastic shows the following: For primary intra-abdominal disease, in which clearly the majority belong to the Non-lymphoblastic histology, with a total of 50 patients, the disease-free survival was 67%; for lymphoblastic histology with 5 patients, the actuarial disease-free survival was 100%. For primary mediastinal with 24 patients with diffuse lymphoblastic histology the disease-free survival was 95%, and in 13 patients with Non-lymphoblastic histology a disease-free survival of 83%.(ABSTRACT TRUNCATED AT 250 WORDS)