RNA interference (RNAi) is an efficient process of posttranscriptional gene silencing. In recent years it has been developed into a new technology in biopharmaceutical fields of science. RNAi products include short interference RNA (siRNA) but also short hairpin RNA (shRNA), bifunctional short hairpin RNA (bi-shRNA) and microRNA (miRNA). They combine with homologous fragments of the mRNA and cause its degradation. It results in inhibition of protein synthesis, or in mutation in the gene encoding it. RNAi has been used in analysis of genomes and creation of new animal models to test drugs. From the pharmaceutical point of view, what is the most important is its therapeutic application. So far the basic and clinical research has been focused on the following targets: macular degeneration, cancer and antiviral therapy. But there are also reports on clinical trials in asthma, hypercholesterolemia and genetic diseases such as inherited skin disorders and amyloidosis. Among over 20 therapeutics that reached clinical trials, only few are still investigated. Another few are clinical candidates. The review focuses on RNAi products under clinical evaluation and their most promising new applications.