PURPOSE We analyzed prognostic factors in 80 adult patients with lymphoblastic lymphoma (LBL). PATIENTS AND METHODS Twenty-one patients received six monthly courses of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) and maintenance chemotherapy for 12 months. The LNH-84 protocol (30 patients) consisted of four courses of high-dose CHOP followed by consolidation for 4 months. Both FRALLE (22 patients) and LALA (seven patients) protocols were two intensive chemotherapy regimens for acute lymphoblastic leukemia (ALL) that included an induction with daunorubicin, vincristine, cyclophosphamide, prednisolone (and asparaginase for the FRALLE regimen), consolidation, and maintenance chemotherapy that lasted for 2 years. RESULTS Sixty-six patients (82%) achieved a complete remission (CR). The CR duration rate and overall survival rate at 30 months were estimated to be 46% and 51%, respectively, with a median follow-up of 55 months. Only two of 37 relapses occurred after 26 months. Chemotherapy protocol did not influence CR rate, CR duration, and survival. A higher CR rate was associated with an age of less than 40 years, lactic dehydrogenase (LDH) level of less than two times the upper limits of normal, and no or one extranodal site of disease. Short survival was associated with a failure to achieve CR, age older than 40 years, B symptoms, LDH level more than two times the upper limits of normal, and hemoglobin level of less than 100 g/L. Bone marrow involvement had no prognostic value. We could not evaluate precisely the prognostic value of Ann Arbor stage because inclusion criteria differed among treatment groups. CONCLUSION Our findings suggest that age and LDH are two important pretreatment prognostic factors for adult LBL, and that the optimal prognostic staging system remains a controversial issue.