Forty-one adult patients with acute myelogenous leukaemia entered remission induced by daunorubicin and cytosine arabinoside, and subsequently received 6 weeks' consolidation therapy with cyclophosphamide plus 6-thioguanine. They were then randomized to either immunotherapy consisting of intradermal BCG plus allogeneic cells or to "no maintenance". Patients receiving immunotherapy had significantly longer remission (P = 0.039) and survival from remission (P = 0.044) as assessed by the log-rank test. The median duration of first remission for 21 patients receiving immunotherapy was 35.14 weeks, compared with 19.71 weeks for 20 patients on no maintenance, and the median survival from remission was doubled in patients receiving immunotherapy. The value of adequate consolidation chemotherapy is confirmed by the comparatively long first remissions in both groups compared with our previous trials, whilst avoidance of maintenance chemotherapy possibly allowed frequent second remissions and similar post-relapse survival in patients from both treatment arms.