Analyses of healthy donors of granulocyte colony-stimulating factor (G-CSF) mobilized hematopoietic stem and progenitor cells (HSPCs) and of patients undergoing autologous stem cell transplantation have suggested that individuals harboring the CXCL12-A allele mobilize a higher number of CD34 + HSPCs after G-CSF administration. We typed 463 healthy unrelated donors (376 men and 87 women) who had received daily subcutaneous injections at a mean dose of 7.36 ± 1.71 μg/kg G-CSF for 5 days for CXCL12 801 G/A using a real-time PCR assay. Interestingly, the median concentration of mobilized CD34 + cells on day 5 was almost identical in donors with the A-allele (79/μL; range, 11 to 249/μL) and the G/G-group (82/μL; range, 15 to 268/μL). In addition, the allelic distribution was not different in donors (n = 11) who mobilized less than 20/μL CD34 + cells. No difference in the overall yield of CD34 + cells in the apheresis product and in the number of CD34 + cells/kg recipient could be detected between both groups. In a multivariate regression model for the endpoint CD34 + cells/μL at day 5, only male sex (regression coefficient, 11.5; 95% confidence interval, 1.7 to 21.2, P = .021) and body mass index as continuous variables (regression coefficient, 3.5; 95% confidence interval, 2.5 to 4.5, P = .0001) but not age, smoking status, or CXCL12 allelic status represented independent variables. Our data derived from a large well-controlled cohort contradict previous analyses suggesting an association between CXCL12 allelic status and the yield of CD34 + HSPC after G-CSF mobilization. Concentration of CD34 + cells in the peripheral blood, the most objective parameter, could not be predicted by CXCL12 genotype.