Matrix metalloproteinases (MMPs) play crucial roles in extravillous trophoblast invasion. In the present study, we examined the possible role of Smad4 and Smad2 in transforming growth factor (TGF)-beta1-induced MMP-2 expression, using the well-established invasive extravillous trophoblast cell line HTR-8/SVneo. Recombinant sense Smad4 or Smad2 retroviral vectors were constructed by inserting full-length Smad4 or Smad2 cDNA into pLXSN retroviral vector. Stable PT67 packaging cell clones were isolated and viral supernatants were used to infect HTR-8/SVneo cells. Effects of retroviral expression of Smad4 and Smad2 on TGF-beta1-regulated MMP-2 expression were assessed by semi-quantitative reverse transcription-polymerase chain reaction and gelatin zymography. The results showed that over-expression of Smad4 augmented MMP-2 mRNA abundance and the secretion of pro-MMP-2, and mimicked the inductive effect of TGF-beta1 on the production of MMP-2. However, retrovirus-mediated sense Smad2 gene transfer had no effect. These findings suggest that Smad4, but not Smad2, mediates TGF-beta1-induced MMP-2 expression in invasive extravillous trophoblasts.