Tumorigenesis is always accompanied by alterations of the microenvironment in the respective tissue. The tumor microenvironment represents a heterogeneous complex, in which cell proliferation, diff erentiation, necrosis or apoptosis are regulated by various extracellular stimuli, and it can also lead to development of an aggressive phenotype of tumor cells. Influence of tumor microenvironment is also often connected with resistance to frequently used therapeutic procedures. Specifics of the tumor microenvironment are closely associated with the structural and functional abnormalities of tumor microvessels and altered cellular metabolism. Moreover, changes such as increase in glycolysis, elevated glucose uptake, production of lactate and CO2, and presence of hypoxic regions and regions with acidic pH are typical features of tumor tissues. At present, there is a lot of methods for in vitro simulation and investigation of some of these specific conditions, and a number of new methods are being developed. A detailed understanding of the specifics of the tumor microenvironment should increasingly improve the development of new treatment possibilities of human cancers.