This is a double-blind randomized placebo-controlled trial to evaluate the efficacy and safety of granulocyte-macrophage colony-stimulating-factor (GM-CSF) after dose-intensive cyclophosphamide, etoposide, and clspiatln (DEEP). Fifty-six patients with lymphoma or breast carcinoma were randomized to receive GM-CSF 250 pglm2 or placebo subcutaneously (SC) every 12 hr after each course of DEEP until recovety of absolute neutrophii count (ANC) of 1.5 x 10Β°/L. Each patient was to receive three courses of DICEP. There were 28 patients in each group. The median duration of ANC below 0.5 x 10% was 10 versus 12 days for Course 1 (P = O.OlO), 10 versus 12 days for Course 2 (P = 0.248), and 16.5 versus 15 days for Course 3 (P = 0.126); platelet counts below 20 x 10B/L was 4 versus 4 days for Course 1 (P = 0.586), 8.5 versus 7 days for Course 2 (P = 0.013), and 23.5 versus 10.5 days for Course 3 (P = 0.104); hospitalization for patients readmitted with cytopenic fever were 4 versus 8 days for Course 1 (P = 0.035); 7 versus 6 days for Course 2 (P = 0.692); and 8 versus 12 days for Course 3 (P = 0.884) in the GM-CSF and placebo group, respectively. GM-CSF significantly shortens the duration of neutropenia and readmission only during the flrst course of DICEP. There was a delay in platelet recovery and an increase in transfusion requirement during subsequent courses In the GM-CSF group. The result cautions the routine use of lineage specific hematopoletic growth factors In supportlng repeated cycles of dose-intenslve chemotherapy.