The invention relates to a double-stranded ribonucleic acid (dsRNA) for inhibiting the expression of the Eg5 gene (Eg5 gene), comprising an antisense strand having a nucleotide sequence which is less than 30 nucleotides in length, generally 19-25 nucleotides in length, and which is substantially complementary to at least a part of the Eg5 gene. The invention also relates to a pharmaceutical composition comprising the dsRNA together with a pharmaceutically acceptable carrier methods for treating diseases caused by Eg5 expression and the expression of the Eg5 gene using the pharmaceutical composition and methods for inhibiting the expression of the Eg5 gene in a cell.
