This randomized, controlled study compared the ability to mobilize and collect an optimal target yield of 5 x 10(6) CD34+ cells/kg using stem cell factor (SCF; 20 microg/kg/day) plus filgrastim (G-CSF; 10 microg/kg/day) vs filgrastim alone (10 microg/kg/day) in 102 patients diagnosed with non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD), who were prospectively defined as being heavily pretreated. Leukapheresis began on day 5 of cytokine administration and continued daily until the target yield was reached, or until a maximum of five leukaphereses had been performed. Compared with the filgrastim-alone group (n = 54), the SCF plus filgrastim group (n = 48) showed an increase in the proportion of patients reaching the target yield within five leukaphereses (44% vs 17%, P = 0.002); reduction in the number of leukaphereses required to reach the target yield (P = 0.003); reduction in the proportion of patients failing to reach a minimum yield of 1 x 10(6) CD34+ cells/kg to proceed to transplant (16% vs 26%, P = NS); increase in the median yield of CD34+ cells per leukapheresis (0.73 x 10(6)/kg vs 0.48 x 10(6)/kg, P = 0.04); and an increase in the median total CD34+ cells collected within five leukaphereses (3.6 x 10(6)/kg vs 2.4 x 10(6)/kg, P = 0.05). All patients receiving SCF were premedicated (antihistamines and albuterol), and treatment was generally well tolerated. Five patients experienced severe mast cell-mediated reactions, none of which were life-threatening. In this study of heavily pretreated lymphoma patients, SCF plus filgrastim was more effective than filgrastim alone for mobilizing PBPC for harvesting and transplantation after high-dose chemotherapy.