Forty molar and non-molar placentas with hydropic changes (14 complete moles, 14 partial moles, and 12 hydropic non-molar placentas) were examined immunohistochemically for expression of oncoproteins p53 and Bcl-2. The data were evaluated to determine if p53 and Bcl-2 expression could aid in differentiating molar from non-molar pregnancies on the one hand and complete mole from partial mole on the other. Thirteen out of fourteen complete moles showed p53 expression (93%), 8 of the 14 partial moles expressed p53 (57%), and none of the non-molar pregnancies expressed p53 in the extravillous intermediate trophoblasts. Regarding Bcl-2, the syncytiotrophoblasts of most molar and non-molar placentas showed strong and diffuse positivity. These results suggest that p53 expression can be used as a distinguishing parameter between complete moles and placentas with hydropic changes on the one hand and to a lesser extent between partial moles and placentas with hydropic changes on the other hand. Bcl-2 cannot be used in the same way as p53.