Objective — to evaluate the effectiveness of oral route of melatonin administration in the treatment of surgically induced endometriosis of female Wistar rats. Material and methods. 33 mature female rats aged 10 to 12 weeks were included into the study. All the experimental animals underwent 3 consecutive surgical interventions. The first stage was the formation of endometriosis model via laparotomy. On the 14th day from the beginning of the experiment the formed foci were evaluated by laparoscopic access with subsequent randomization of animals into groups. The main group consisted of 11 animals that received melatonin. The control group included 12 animals without treatment. The comparison group included 10 animals that were treated with dienogest. At the final stage, after three weeks of therapy, the animals were removed from the experiment and autopsy was performed. Results. After the application of melatonin, the area of 18 from 22 heterotopies significantly decreased. In 44.4% of cases there was a complete resorption of foci. In the control group after the end of the experiment, there was a significant increase of heterotopies in 86.9% of cases, in 8.7% of cases there was a regression of heterotopies. In the comparison group, after dienogest therapy, the area of 85% of heterotopias significantly decreased, and in 58.8% complete resorption of endometriosis foci was noted. Conclusion. On the basis of experimental work it was found that the effectiveness of melatonin in the treatment of endometriosis is only slightly lower than the results obtained during treatment with dienogest, which is considered to be a specific and highly effective hormonal therapy of the disease. Thus, the use of melatonin can be considered as a targeted therapy of endometriosis in the future.