Among 164 patients with acute lymphoblastic leukemia (ALL) (age greater than 11 years) induced into complete remission at four hospitals in Italy and The Netherlands between 1971-1977, 49 survived for more than three years in continuous complete remission. Features at diagnosis of the 49 long-term survivors were compared with those of the parent group. The long-term survivors presented with significantly lower leukocyte counts and were slightly younger. Late relapses occurred in nine patients after 37-91 months from remission. Of the 45 patients who had all treatment stopped after 24-60 months of continuous remission, seven have relapsed. Relapses, mainly in the marrow, occurred 4-32 months after cessation of therapy, the risk of relapse being greatest in the first year and dropping to zero by the fourth year. ALL appears curable in approximately one fifth of adolescents and adults entering complete remission with adequate chemotherapy.