Background. Ovarian heterotopias are quite successfully diagnosed with ultrasound examinations. Considering the high risk of spread of the disease, as well as reproductive consequences (infertility, pelvic adhesive processes, chronic pelvic pain syndrome, dysmenorrhea), early differential diagnosis of endometrioid cysts and, accordingly, early initiation of treatment are of particular importance.Objective: to combine ultrasound criteria using 3D visualization and the content of biomarkers to verify stage 1–2 endometrioid ovarian cysts.Material and methods. In 59 infertile women with endometrioid ovarian cysts, in the dynamics of the menstrual cycle, ultrasound examinations were performed using Acuson S2000 (Siemens, Germany) and Voluson E8 (General Electric, USA) with the possibility of Doppler measurements and three-dimensional reconstruction of tissue images. Also, in laboratories “Invitro”, “Hemotest”, “Nauka” (Samara, Russia) the biomarkers were determined: interleukins IL-1β, IL-6, cancer antigen 125 (CA-125), human epididymis protein 4 (HE4) and the index by Risk of Ovarian Malignancy Algorithm (ROMA). The control group included 195 fertile women of reproductive age. In patients with endometrioid cysts, the diagnosis was subsequently confirmed morphologically.Results. Small unilateral and bilateral ovarian cysts corresponding to stage 1–2 endometriosis by revised American Fertility Society classification (rAFS) were clearly differentiated in 56 (94.9%) patients, in 3 (5.4%) of them the ultrasound result was questionable. In 48 (81.4%) women the lesion was unilateral and in 11 (18.6%) it was bilateral. The structure of cystic formations in all cases was hypoechoic, heterogeneous, in 36 (61.0%) cases it was finely cellular, without blood flow.Conclusion. Ovarian endometriomas in “gray scale” are round formations of reduced echogenicity and fine suspension, with an even, clear contour, not fused with the surrounding tissues, avascular, changing size depending on menstrual cycle phase. An ovarian mass may have a capsule with locus signals on Doppler. The sensitivity of ultrasound examination in “gray scale” in the presence of an endometrioid cyst is 94.6%.