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