Extensive small-cell lung cancer (SCLC) is commonly treated with multiple cycles of chemotherapy. Reducing the time interval between cycles of chemotherapy (dose-dense chemotherapy) may improve outcomes in the treatment of extensive SCLC, as it has in other chemosensitive malignancies. To evaluate the feasibility of dose-dense chemotherapy in patients with extensive SCLC, this study evaluates a dose-dense doxorubicin/cyclophosphamide/etoposide (ACE) regimen, supported by the once-per-cycle administration of the hematopoietic growth factor pegfilgrastim. Patients received up to six 14-day cycles of ACE chemotherapy (doxorubicin 40 mg/m,(2) cyclophosphamide 1000 mg/m(2), etoposide 120 mg/m(2) on day 1 IV, plus oral etoposide 240 mg/m(2) daily on days 2-3). On day 4 of each cycle, patients received pegfilgrastim 6 mg by subcutaneous injection. Of 30 patients enrolled, 27 started chemotherapy and received pegfilgrastim. Full-dose, on-schedule chemotherapy was given to all 22 patients starting cycle 2, and in 107 (88%) of 121 cycles. Eighteen of the 27 patients (67%) received full-dose, on-schedule chemotherapy for all 6 cycles. The overall response rate was 17/27 (63%). Nine patients (33%) experienced hematologic toxicities that investigators considered severe or life-threatening. Four patients (15%) had febrile neutropenia. Full-dose, on-schedule dose-dense ACE chemotherapy is feasible with once-per-cycle pegfilgrastim support in extensive SCLC.