The goal of our research was to find the prognostic significance of the epidermal growth factor receptor (EGFR) in the hyperplastic endometrium. Immunohistochemical study of morphological material (endometrial scrap) was conducted in order to reveal the EGFR expression (in 35 patients). The study of consistence of melatonin (universal antiproliferative and anticancerogenic hormone) in patients' blood serum was performed as well (using ELISA method). The numeric data of investigation were processed statistically using the SPSS-12 program and IBM SPSS Statistics, 20. According to received results, the more complicated the type of endometrial hyperplasia is, the stronger EGFR expression is and the more melatonin consistence is reduced in blood plasma. However, sometimes much lower level of melatonin not only in case of complex hyperplasia (with atypia), but also in case of simple hyperplasia (without atypia) was observed. In addition, melatonin consistence is in norm not only in case of simple hyperplasia, but also in case of complex hyperplasia. Also, unimportant reduction of melatonin level is seen in plasma in case of both types of endometrial hyperplasia (without atypia): if, for example, in simple hyperplasia, this slight reduction of melatonin level in plasma is seen in condition of sharp EGFR expression, the same amount reduction of plasmatic melatonin in complex hyperplasia is seen in condition of weak EGFR expression. To sum up: in case of simple endometrial hyperplasia without atypia, reduction of plasma melatonin level should be a bad prognostic indicator and this condition can be followed by transformation of hyperplasia into atypical form; the normal plasmatic level of melatonin in complex endometrial hyperplasia without atypia (in condition of weak EGFR expression) should be a good prognostic indicator; unimportant reduction of plasma melatonin level and in addition, EGFR sharp expression in simple hyperplasia, is probably the sign, that hyperplasia can change and become complex; however, the same indicators of plasma melatonin level (on the background of weak EGFR expression) in complex hyperplasia (without atypia) should not indicate the poor prognosis.