Abstract: The present invention relates to a method for the delivery of therapeutic oligonucleotides to bone marrow, and in particular delivery of siRNA to a subset of bone marrow cells. The method comprises systemically administering siRNA to a subject in need thereof, to reduce or inhibit expression of a gene associated with a disease or disorder or to symptoms associated with a disease or disorder associated with the cells. The invention further relates to chemically modified siRNA compounds, to pharmaceutical compositions comprising such compounds and to methods of using such compounds and compositions in the treatment of disease.