Adenoviruses do not alter the ability of committed hematopoietic progenitor cells to form colonies in methylcellulose. Blood mononuclear cells obtained after treatment of patients undergoing hematopoietic stem cell mobilization with granulocyte colony-stimulating factor (G-CSF) were infected with Ad5dl309 at an moi of 100 for the indicated periods of time and plated in methylcellulose (in the presence of IL-3, granulocyte-macrophage colony-stimulating factor [GM-CSF], and erythropoietin [Epo]) using commercially available media (Stem Cell Technologies, Vancouver, British Columbia, Canada). Colonies (colony-forming unit-erythroid [CFU-e], burst-forming unit-erythroid [BFU-e], colony-forming unit–granulocyte-macrophage [CFU-GM]) were counted at 14 days. (−) Uninfected; (+) infected with Ad5dl309.