During human placental development, cytotrophoblast stem cells differentiate and invade the uterus. Simultaneously, the cells modulate their expression of several classes of stage-specific antigens that mark transitions in the differentiation process and play a role in either uterine invasion (integrin cell-extracellular matrix receptors and matrix metalloproteinase-9) or immune interactions (HLA-G). The pregnancy disease pre-eclampsia is associated with shallow cytotrophoblast invasion. Previously we showed, by immunofluorescence localization on placental tissue, that in pre-eclampsia invasive cytotrophoblasts fail to properly modulate their integrin repertoire. This finding suggests possible abnormalities in the differentiation pathway that leads to uterine invasion. Here we used a culture system that supports this differentiation process to compare the differentiative and invasive potential of cytotrophoblasts obtained from control (n = 8, 22 to 38 weeks) and pre-eclamptic (n = 9, 24 to 38 weeks) placentas. In culture, the cells from pre-eclamptic placentas failed to properly modulate alpha1 integrin and matrix metalloproteinase-9 expression at the protein and mRNA levels. Their invasive potential was also greatly reduced. Likewise, the cells failed to up-regulate HLA-G protein and mRNA expression. These results suggest that defective cytotrophoblast differentiation/invasion can have significant consequences to the outcome of human pregnancy (ie, development of pre-eclampsia) and that, by the time delivery becomes necessary, the defect is not reversed by removing the cells from the maternal environment.