Small cell lung cancer (SCLC) is a frequent and aggressive tumor characterized by its major sensitivity to chemotherapy since 80% of the patients respond dramatically to the treatment. Nevertheless, the majority of them eventually die from their cancer. We have addressed the effect of late intensification with autologous bone marrow transplantation on SCLC through a randomized clinical trial. This study included 101 patients, 45 of whom could be randomized to either conventional post-induction therapy or late intensification. Of the 32 patients with limited disease, patients who did not receive intensification relapsed on a median of 10 weeks compared with 35 weeks for patients who received intensification (p = 0.001). An important observation was that there was no patient disease free at 1 year in the group that did not receive intensification whereas there were patients who were free of disease up to 271 weeks in the group receiving late intensification. To improve upon these results we have developed a panel of anti-lung cancer monoclonal antibodies that we use for the detection of occult cancerous disease in the bone marrow and for the in vitro elimination of clonogenic tumor cells contaminating the marrow graft. In addition we are monitoring the immune defect induced by ABMT and its compensation by an in vitro recombinant human IL-2 perfusion. Finally we have devised a new induction and intensification chemotherapy regimens with different drugs in order to prevent multidrug resistance. These new tools are currently under investigation in the clinical setting.