The invention provides methods and compositions for gene silencing by RNA interference. In particular, the invention provides methods for gene silencing or RNA knockdown using small interfering RNAs (siRNAs) having partial sequence homology to its target gene. The invention also provides methods for identifying common and/or differential responses to a plurality of different siRNAs targeting a gene. The invention also provides methods for evaluating the relative activity of the two strands of an siRNA. The invention further provides methods of designing siRNAs for gene silencing. The invention further provides methods of using siRNAs as therapeutics for treatment of diseases.
