Several serious infections, such as hepatitis C, dengue fever, West Nile encephalitis, tick-borne encephalitis or yellow fever have been caused by viruses from Flaviviridae family. Until now, no effective chemotherapeutics or vaccines have been available for most of them. Only vaccines against yellow fever and tick-borne encephalitis have been developed. The search for direct antiviral agents that specifically target essential components of virus replication system has been the focus of intense research efforts. The most advanced research is evident in the specifically targeted antiviral therapy for HCV (STAT-C). Owing to the use of modern structure-based drug design techniques, small molecules that inhibit the HCV NS3 protease have emerged as the most promising of the STAT-C therapies. Telaprevir and boceprevir – two peptomimetic inhibitors are in phase III clinical studies. The synthesis of telaprevir and its mechanism of action has been presented.