1,2 Models of the development of cytotoxic drug resistance suggest that maximal initial treatment will reduce the risk of relapse.3,4 Although small cell lung cancer (SCLC) is the histologic type most sensitive to combination chemotherapy, the majority of SCLC patients relapse with chemoresistant tumors. Circumvention of this secondary chemoresistance has been addressed using different treatment modalities.In a recent study, patients with limited-disease SCLC were randomly assigned to receive higher-or lower-dose cyclophosphamide and cisplatin during the first course of a cisplatin, etoposide, doxorubicin and cyclophosphamide regimen followed by five additional cycles at standard doses.5 A moderate increase in the cisplatin and cyclophosphamide doses during the first course resulted in a 17% increase in 2-year survival. However, myelosuppression is the limiting toxicity for this chemotherapy regimen.For the majority of drugs, myelosuppression is the initial dose-limiting toxicity. While hematopoietic growth factors have been utilized to reduce the toxicity and improve delivery of the planned dose, only a modest increase in dose intensity can be achieved.Recently, peripheral blood stem cells (PBSCs) have been used as a source of stem cells and shown to restore hematopoietic functions rapidly after PBSC autografting. Highdose chemotherapy with PBSC rescue has been used for leukemia and lymphoma, but for most chemosensitive solid tumors, a single high-dose chemotherapy as late intensification does not appear to prolong survival. 6 Since adjustments of the dose of cytotoxic drugs, as well as shortening of the intervals between courses, can increase dose intensity, multicyclic chemotherapy may offer the opportunity to maximize dose intensity of the treatment.