Changes in blood dendritic cell (BDC) counts (CD123hiBDC and CD11c+BDC) and expression of CD62L, CCR7, and CD49d were analyzed in healthy donors, multiple myeloma (MM), and non-Hodgkin lymphoma (NHL) patients, who received granulocyte-colony stimulating factor (G-CSF) containing peripheral blood stem cell (PBSC) mobilization protocols. Low-dose G-CSF in healthy donors (8-10 μg/kg/d subcutaneously) and high-dose G-CSF in patients (30 μg/kg/d) increased CD123hiBDC (2- to 22-fold, mean 3.7 × 106/L-17.7 × 106/L and 1.9 × 106/L-12.0 × 106/L) in healthy donors and MM but decreased CD11c+BDC (2- to 10-fold, mean 5.7 × 106/L-1.6 × 106/L) in NHL patients, on the day of apheresis, compared with steady state. After apheresis, CD123hiBDC counts remained high, whereas low CD11c+BDC counts tended to recover in the following 2-5 days. Down-regulation of CD62L and up-regulation of CCR7 on CD123hiBDC were found in most healthy donors and MM patients. CD49d expression was unchanged. Thus, PBSC mobilization may change BDC counts by altering molecules necessary for BDC homing from blood into tissues.