Ovary endometriosis is a wide-spread disease that effects reproductive-aged women, causes reproductive dysfunction, and lowers quality of life. The objective was to observe the pathomorphologic structure of ovary endometriosis, estimate its proliferative potential. Methods and patients. 130 women with ovary endometriosis were observed. Diagnosis was verified by the histological analysis of surgical material after endoscopic elimination of lesions. Women were divided into groups according to the r-AFS classification. Pathomorphologic and immune hystochemical test, determination of Ki-67 and IV type collagens were performed. Results. Women who had I-II stages of ovary endometriosis in the samples was evaluated mild intensiveness of IV type collagen lightning in vessel basal membranes of ectopic endometrioid lesions. Due to the presence of this type of collagens basal membranes are characterized with mechanic stability. While determining proliferation activity marker Ki-67 expression, mitotic index of epiteliocytes was 6,7Â±0,02%, of stromal cells 5,5Â±0,03%. In women with III-IV stages of the disease different variants of immunohystochemical markers expression were detected. In first occasion in cytogene stroma small amount of microcirculatory vessels with thickened or sclerotic walls were found. IV type collagen was determined in increased contain, mitotic index of epiteliocytes was 5,2Â±0,04%, of stromal cells 4,8 Â±0,05%. In second variant vessel component was defined in significant amount. IV type collagens in vessel wall basal membranes were determined in more mild lightening. Mitotic index of epiteliocytes was 7,8Â±0,04%, of stromal cells 8,2Â±0,05%, that testified increased proliferative activity and probably higher risk of malignisation as well as could be considered more likely to relapse. Conclusions. Different variants of ovary endometrioma pathomorphological structure were described. Observed changes help to explain individual distinction in ovary endometriosis progression.