The commercial potential of RNAi is assessed on the basis of successful translation of technology into applications in three areas: (1) drug discovery and research-currently the biggest segment; (2) potential therapeutic applications; and (3) the role of microRNA in molecular diagnostics. RNAi is an important method for analyzing gene function and identifying new drug targets that use dsRNA to knock down or silence specific genes. Sets of siRNAs focused on a specific gene class (siRNA libraries) have the capacity to greatly increase the pace of pathway analysis and functional genomics. RNAi plays an important role in drug discovery by facilitating target validation. The discovery of the role of microRNA (miRNAs) in various pathological processes opens up possible applications in molecular diagnostics, particularly that of cancer. The advantages of RNAi-based therapeutics over traditional pharmaceuticals include the capability for more specific therapies with small molecule siRNA. Drawbacks include the development of resistance in cancer and viral infections as well as the interferon effect. RNAi is closely related to gene therapy and the vectors developed for gene therapy are also being used for delivery of siRNAs. RNAi, along with other related technologies, will contribute to the development of personalised medicine. Although none of the RNAi-based drugs is in the market yet, some are in clinical trials. By the year 2010 the market for RNAi-based drugs is expected to be worth 3.5 billion dollars and is expected to expand to 10.5 billion dollars by the year 2015.