Gliomas are the most frequently occurring primary tumor in the brain. The most malignant form of glioma, glioblastoma multiforme (GBM), is characterized by rapid and invasive growth and is restricted to the central nervous system (CNS). The transforming growth factor beta 2 (TGF beta 2)/small mothers against decapentaplegic (Smad) signaling pathway is important, not only in GBM cell metabolism and invasion, but also in GBM cell proliferation. However, the functions of the downstream mediators of the TGF beta 2/Smads signaling pathway remain to be fully elucidated. In the present study, short hairpin (sh) RNA interference was used to specifically inhibit the expression of Smad2 and Smad3 in the TGF beta 2/Smad signaling pathway to investigate the effects of shRNA on the proliferation of human GBM cells. The results demonstrated that knockdown of either Smad2 or Smad3 enhanced cellular proliferation. Additionally, the key target genes involved in GBM cell proliferation, induced by TGF beta 2, were found to be dependent on Smad3, but not Smad2.