Background: The hydatiform mole is charcaterized by a pathological proliferation of the trophoblast. Its evaluation could predict the progression to gestational trophoblastic neoplasia. The aim of the study was the analysis of the proliferative activity of the villous trophoblast in the molar vs non-molar lesions. Material and methods: p-57 and Ki-67 were evaluated by immunohistochemistry in 15 cases of hydatidiform mole and 18 cases of abortions. Results: The hydatidiform mole was divided based on the immunoexpression of anti-p57 into: complete (8 cases) and partial type (7 cases). The distribution score of Ki67 immunoreactivity in the villous cytotrophoblast was: complete mole: +3 – 8 cases; partial mole: +1 – 1 case, +2 – 3 cases, +3 – 3 cases; abortions on social indications: +1 – 6 cases, +2 – 9 cases; +3 – 2 cases. The mean and standard deviations were: 2.88±0.354; 2.29±0.756 and 1.82±0.728, respectively. The following statistical correlations were determined: complete vs partial mole (p=0.014), complete mole vs abortion (p<0.01) and overall cases of mole vs abortion (p=0.000034). Conclusions: Villous cytotrophoblast proliferative activity is high in the complete hydatidiform mole, and the immunoreactivity distribution index is highly positive and statistically true in the molar versus non-molar group. Immunohistochemical evaluation of Ki-67 in molar pathology is useful in differential diagnosis as a complementary method.