Between 1974 and 1984 69 adults with acute lymphoblastic leukaemia (ALL) were treated with two different protocols. Fifty-four (78%) of the patients entered complete remission (CR); 27 of these then received a consolidation protocol consisting of daunorubicin, cytosine arabinoside and 6-thioguanine, followed by two courses of intravenous methotrexate 500 mg m-2 with folinic acid rescue. All patients received intrathecal methotrexate and cranial irradiation (24 Gy) followed by maintenance therapy with 6-mercaptopurine and methotrexate for at least 2 years. The median survival for all patients was 23 months from the time of presentation with an actuarial 5-year survival of 21%. The actuarial chance of surviving 5 years in CR for patients receiving the consolidation protocol was 38% compared to 19% for patients receiving no consolidation (P = NS). Only patient age and white cell count at presentation were found to influence the chance of achieving CR and the chance of overall survival. The presence or absence of c-ALL antigen did not influence prognosis. Patients younger than 35 years with low white cell counts at presentation (less than 10 X 10(9)1(-1] had a particularly good prognosis but no patient with T-ALL and no patient older than 50 years old at diagnosis survived more than 18 months.