Hsp90 is highly evolutionary conserved molecular chaperone who is present in all prokaryotic and eukaryotic cells, with the exception of arheabacteria. It belongs to a group of heat shock proteins, molecular chaperons whose function is to secure correct protein folding, preventing unspecific protein interactions and forming protein complexes. Hsp90 regulates the stability and function of more than 200 clients, many of which are included in cellular signalling, regulation of cell cycle and cell survival. Clients who are involved in these processes also have important role in oncogenesis. Inhibition of Hsp90 results in ubiquitinilation and degradation of mentioned clients. Advantage of Hsp90 inhibitors over many other chemotherapeutics is that they accomplish simultaneous disruption of multiple signalling pathways that are of great importance for growth and survival of cancer cells. Inhibition is accomplished by compounds that selectively bind to the ATP binding spot in N domain of Hsp90 and prevent conformational changes that are necessary for protein activity. Hsp90 monotherapy showed weak results in treatment of solid tumors, however combining Hsp90 inhibitors with other cytostatic drugs showed satisfying results. At the moment there are couple of Hsp90 inhibitors in 2nd and 3rd phase of clinical trials for treatment of non-small cell lung cancer, HER2+ breast cancer and multiple myeloma. The future of tumor treatment with Hsp90 inhibitors will be based on combining them with other cytostatics, which results in synergistic effect.