Purpose: This study's main aim was to assess the effect of 2 mobilization regimens (granulocyte colony-stimulating factor [G-CSF] and chemotherapy vs. G-CSF alone) on the yield of CD34(+) cells in the apheresis components of patients with lymphoid malignancy. We also sought to identify possible predictors of CD34(+) cell yield in the apheresis components. Patients and Methods: CD34(+) cells were mobilized and harvested from 89 patients with non-Hodgkin lymphoma (n = 62) or Hodgkin disease (n = 27). Forty-one patients (46.1%) were mobilized with G-CSF, and 48 (53.9%) were mobilized with chemotherapy and G-CSF. Univariate and multivariate analyses were used to examine potential predictors of the CD34(+) cell yield (collection of > 2.7 x 10(6) cells/kg), such as the number of peripheral CD34(+) cells, age, sex, diagnosis, disease stage, weight, bone marrow status at baseline, mononuclear cells, white blood cells, and platelet counts. Results: The median patient age was 41 years (range, 12-66 years), and the median patient weight was 72 kg (range, 44-123 kg). Mobilization of peripheral blood progenitor cells (PBPCs) was superior when using chemotherapy and G-CSF versus G-CSF alone (3.6 x 10(6) cells/kg vs. 2.2 x 10(6) cells/kg; P =.001). CD34(+) cell counts and platelet counts in the peripheral, blood significantly correlated with CD34(+) yield (P<.01 and P=.009, respectively). The yield was also significantly affected by weight, diagnosis, mobilization regimen, and baseline bone marrow status (P =.021, P=.05, P =.002, and P =.043, respectively). Conclusion: Many factors influence harvesting of PBPCs, including diagnosis, bone marrow status at baseline, patient weight, and the type of mobilization regimen. The number of CD34(+) cells in the peripheral blood can be used to predict the timing of apheresis and optimize yield.