The present invention relates to a double-stranded ribonucleic acid (dsRNA) for inhibiting the expression of an anti-apoptotic gene, comprising a complementary RNA strand having a nucleotide sequence which is less that 25 nucleotides in length and which is substantially identical to at least a part of an apoptotic gene, such as a Bcl gene. The invention also relates to a pharmaceutical composition comprising the dsRNA together with a pharmaceutically acceptable carrier; methods for treating diseases caused by the expression of an anti-apoptotic gene using the pharmaceutical composition; and methods for inhibiting the expression of an anti-apoptotic gene in a cell.