This paper analyzes the clinicopathological features of 31 consecutive adult patients with lymphoblastic lymphoma (LBL) and reports on our experience in treating them with two successive multidrug programs analogous to those used in acute lymphoblastic leukemia (ALL) in adults. Protocol 1 (18 patients) consisted of an intensive four-drug induction therapy (daunorubicin, cyclophosphamide, vincristine, prednisone), CNS prophylaxis (cranial irradiation and intrathecal methotrexate), and continuous maintenance with methotrexate and mercaptopurine for three years, with periodical reinductions with vincristine and prednisone. Protocol 2 (13 patients) included a similar induction regimen (doxorubicin instead of daunorubicin, dexamethasone instead of prednisone), followed by post-remission intensification with alternating courses of non-cross-resistant agents (amsacrine and high dose cytarabine; vincristine, cyclophosphamide and doxorubicin; etoposide and conventional dose cytarabine) given in a cyclical eight-month program. CNS prophylaxis consisted of intrathecal methotrexate and systemic high-dose cytarabine. The patient characteristics of the two therapy groups were comparable. The complete remission (CR) rate for both groups was 77%, with a median overall and relapse-free survival of 18 and 29 months, respectively. The three-year overall survival of complete remitters was 59%. No correlation was found between CR rate and age, mediastinal, or bone marrow involvement. Stage I disease had a significantly higher CR rate (100%) than did stages II-IV (64%). Leukemic evolution occurred in 32% of cases, within a median time of 11 months from diagnosis; meningeal disease developed in six cases (19%); in four of them leukemia was concomitant. No significant differences were found between the two successive treatments for CR rate, survival, CNS relapses or toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)