15 patients with small-cell lung cancer were treated with an "accelerated" chemotherapy consisting of standard-dose cyclophosphamide-doxorubicin-etoposide administered every 15 days (as opposed to the usual 21-day intervals) along with granulocyte-macrophage colony stimulating factor (10 micrograms/kg/day) administered prophylactically subcutaneously from day 4 to 13. The primary objective of this study was to examine the possibility of achieving a 50% dose-intensity increase by a shortening of chemotherapy intervals. 9 patients were not able to complete the planned six courses of chemotherapy owing to cumulative haematological toxicity. In fact, while leukopenia was acceptable and constant during treatment, both thrombocytopenia and anaemia progressively worsened with subsequent courses, becoming particularly severe after the 4th cycle when interruption of the treatment was often required. 13 patients who completed four courses of chemotherapy received a median of 96% of the planned dose-intensity. This corresponded with an average relative dose-intensity actually delivered of 1.44 compared with the planned dose-intensity of a standard cyclophosphamide-doxorubicin-etoposide every 21 days. In conclusion, acceleration of cyclophosphamide-doxorubicin-etoposide chemotherapy combined with granulocyte-macrophage colony stimulating factor can lead to a significant increase of dose-intensity but it is feasible only for a limited number of courses.