RNA interference (RNAi) is a method for silencing gene expression. It is relatively gene-specific, potent, and minimally toxic. For these reasons, RNAi holds great promise for the treatment of haematological malignancies. Much has already been learned about RNAi in the laboratory, although many fundamental questions about its mechanisms remain to be elucidated. For human trials, major hurdles to be overcome include the induction of a nonspecific immune response to RNAi, the selection of the most appropriate targets, the design of more specific molecules, and the assurance of efficient delivery and safety in patients. Translational research efforts are currently well on their way to solving these problems, and will be reviewed here.