The chemotherapy dose-intensity in two adapted German BFM paediatric protocols (BFM 90 and NHL 86) was compared in contemporaneously treated adults <50 years with Burkitt lymphoma and B-cell lymphoma unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma (collectively referred to as BL). In BFM 90, primary prophylaxis with Granulocyte-colony-stimulating factor was used, postinduction treatment was started at granulocytes > or =0.5 x 10(9)/L (> or =1.0 x 10(9)/L in NHL 86) with a higher mean methotrexate dose (2.9 g/m(2)/cycle, n = 23; 1.6 g/m(2)/cycle in NHL 86, n = 22, P < 0.001). Intervals between consecutive treatment-cycles were shorter in BFM 90 (P < 0.001) with no additional toxicity. However, the two-year failure-free survival with BFM 90 (82%) was similar to that achieved with NHL 86 (72%, P = 0.33). We conclude that BFM 90 enables safe intensification of therapy in young adults with BL compared to NHL 86, but registry-based studies are required to further evaluate the antineoplastic effects and cost-effectiveness of the two therapeutic approaches.