Plating efficiency of AdGFP-infected CD34⁺cells measured by colony-forming assays performed in 0.36% agarose, in the presence of IL-3, IL-6, G-CSF, KL, and EPO. CD34⁺cells that were exposed to AdGFP at MOIs <500 had normal plating efficiency. Cells exposed to MOIs >500 demonstrated significant reduction of colony formation. Cell-sorted CD34⁺GFP⁺ cells that were exposed to AdGFP (MOI, 100) before cell sorting, demonstrated normal plating efficiency, suggesting that an adenovector load corresponding to an MOI of 100 does not negatively influence primary plating efficiency of CD34⁺ cells (*P < 0.05 v MOI of 0).