Abstract: The present invention relates to a double-stranded ribonucleic acid (dsRNA) having a nucleotide sequence which is substantially identical to at least a part of a target gene and which is no more than 49, preferably less than 25, nucleotides in length, and which comprises a complementary (antisense) RNA strand having a 1 to 4 nucleotide overhang at the 3?-end and a blunt 5?-end. The invention further relates to a pharmaceutical composition comprising the dsRNA and a pharmaceutically acceptable carrier. The pharmaceutical compositions are useful for inhibiting the expression of a target gene, as well as for treating diseases caused by expression of the target gene, at low dosages (i.e., less than 5 milligrams, preferably less than 25 micrograms, per kg body weight per day). The invention also relates to methods for inhibiting the expression of a target gene, as well as methods for treating diseases caused by the expression of the gene.