We report a series of 34 adult patients with lymphoblastic lymphoma treated at our Institute between 1977 and 1986. At presentation, mediastinal involvement was seen in 76%, extranodal involvement (not including bone marrow) in 20%, stage IV in 53% and circulating blasts in 15%. In the 15 cases where immunological studies were performed, 12 proved to be of T type and the other three lacked both T and B markers. Chemotherapy with acute lymphocytic leukemia (ALL) protocols was given to 58% and lymphoma protocols to the other patients, with CNS prophylaxis given to a total of 28 patients. Although complete remission (CR) was observed overall in 74% of patients, 5 year survival was only 22% (42% in stages I-II and 8% stages III-IV) with improved results seen with recent aggressive anti-leukemic protocols. Five relapsed patients entered second CR and two were still in CR at this time. CNS relapse occurred in a total of eight patients (three without prophylaxis), and was isolated in two of six patients who achieved CR (despite CNS prophylaxis). In an analysis of prognostic factors, only the attainment of a CR was statistically significant (P less than 0.001). Thus we are unable to confirm other studies which demonstrated prognostic variations in this disease and believe that all such patients should receive aggressive chemotherapy with substantial CNS prophylaxis similar to those currently used for ALL.