Acute lymphoblastic leukemia (ALL) in the elderly is characterized by its poor prognosis. Forty patients with ALL, aged 55 years or older, and with good performance status (ECOG <3) were prospectively treated according to an age-adapted regimen: induction therapy was derived from the LALA87 protocol while the feasibility of treatment with interferon combined with chemotherapy was assessed during maintenance. Compared with younger adults treated according to the LALA87 protocol, elderly patients did not present with more adverse prognostic features, except for a lower incidence of T cell ALL (9 vs 31%, P=0.005). There were even less patients with a high leukocyte count (15 vs 38%, P=0.003), a characteristic associated with adverse prognosis while the incidence of Philadelphia-positive (Ph-positive) ALL was not significantly increased compared to younger adults (31 vs 20%, P=0.2). After completion of induction therapy, with or without salvage treatment, 85% (CI: 70-94%) obtained a complete response (CR) while treatment-related mortality during induction was 7.5% (CI: 2-20%). Median overall survival and disease-free survival were 14.3 months and 14 months, respectively, which, although inferior to results achieved in younger adults, compares favorably with available data in the elderly. Treatment with IFN proved feasible in most patients but had to be discontinued in eight patients because of toxicity. Age-adapted treatment improves the prognosis of ALL in the elderly even if, in most cases, a cure cannot be achieved.