Folate receptors (FRs), membrane-bound proteins that bind specifically to folate with high affinity, are overexpressed by various cancer types and are therefore used as targets for delivery of therapeutic agents. Molecular spherical nucleic acids (MSNAs) are dendritic formulations of oligonucleotides (ONs) that may have advantages over linear parent ONs with respect to delivery properties. Here, we assembled folate-decorated MSNAs, site-specifically radiolabeled them, and then biologically evaluated their effects in mice bearing HCC1954 breast cancer xenograft tumors. The biodistribution of intravenously administered