The survival of patients with acute non-lymphoid leukaemias (ANLL) receiving chemotherapy (32 patients) or chemotherapy plus BCG (31 patients) has been compared in a randomized trial which started in Nov 1974. Fresh BCG (Institut Pasteur, Paris) was administered by Heaf gun in the interval of chemotherapy cycles. The overall survival was better in the chemo-immunotherapy group (median duration of survival of 25 months compared to 16 months in the chemotherapy group). However, the first remission duration did not differ (median duration of the 15 and 12 months, respectively). Plateau survival curves were not obtained in either group. A second complete remission was obtained in 7 out of 12 patients with bone marrow relapses in the chemo-immunotherapy group, and only in 2 out of 15 in the chemotherapy group (P less than 0.05). BCG seemed more efficient in patients older than 40 years; no difference was observed according to sex.