There is little evidence on roles of growth factors other than cytokines in expansion of cord blood (CB) stem cells. We aimed to explore a novel approach for expansion, using Substance P (SP) and calcitonin gene-related peptide (CGRP) neuropeptides. CB CD34(+) cells were cultured in different concentrations of SP and/or CGRP in combination with a cytokine cocktail. Phenotypic and functional analysis was performed by flowcytometry and colonogenic assay. Our results show a significant improvement of total expansion of neuropeptide treated cells. There was a selective effect of CGRP on CD34(+) CD133(+) cells, SP on CD34(+) CD45(dim) cells, and 10(- 9) M SP and/or CGRP on expansion of CD34(+) CD38(- ) cells. There was also a tendency for erythroid and granulocyte-myeloid colony formation in SP and CGRP treated cultures, respectively. Supplementation of cytokines with other growth factors, such as neuropeptides, might enable us to overcome the difficulties of ex vivo expansion of CB cells.