Autologous bone marrow transplantation raises the question of the possible reinjection of tumour cells together with marrow. This paper investigates the ability of chemical compounds other than cyclophosphamide derivatives to eradicate small cell lung cancer (SCLC) in bone marrow. The responsiveness of SCLC lines to cis-platinum, doxorubicin, VP16, Celiptium (an ellipticine derivative), Ditercalinium, a new drug belonging to the pyridocarbazole series, and Asta Z were measured in an agar-agar clonogenic assay. Cis-platinum and Ditercalinium exhibited a high tumouricidal effect. The low cloning efficiencies of SCLC lines in an agar-agar clonogenic assay did not allow tumour cells to be detected among bone marrow cells with sufficient sensitivity. Therefore cis-platinum and Ditercalinium were tested on bone marrow-tumour cell mixtures cultured in a liquid medium allowing the detection of one tumour cell per 10(4) bone marrow cells. As cis-platinum exhibited a low myelotoxicity, it is proposed for purging bone marrows of patients with SCLC.