Although previous studies had indicated that the CD8alpha- and CD8alpha+ subtypes of murine dendritic cells (DCs) differ in immediate origin, a recent study found that intravenous transfer of CD8alpha- DCs led to CD8alpha+ DCs in the spleen several days later, suggesting a direct precursor-product relationship. We have repeated these experiments with a balance sheet approach. We find that though a few CD8alpha+ DCs can be generated in such experiments, this is a rare event and could be the result of a contaminant precursor. Most of the immediate precursors of CD8alpha+ DCs are cells that lack the phenotype of a recognizable DC. CD8alpha- DCs and CD8alpha+ DCs are not precursor-product related, though these sublineages may be connected further upstream.