Gene microarray analysis indicated that several components of the transforming growth factor beta receptor (TGF-betaR) signaling pathway are differentially expressed in leiomyoma and myometrium. To validate the microarray results we evaluated the expression of Smads, intracellular proteins that transmit TGF-betaR signals, in leiomyoma and matched myometrium from untreated women, and women who received gonadotropin releasing hormone analogue (GnRHa) therapy. Semi-quantitative RT-PCR, Western blotting and immunohistochemistry indicate that leiomyoma and myometrium expresses receptor-activated Smad3, common Smad4 and inhibitory Smad7, with elevated expression of Smad3, Smad4 and phosphorylated Smad3 (pSmad3) as well as TGF-betaR type I and type II in leiomyoma compared to myometrium (P<0.05). GnRHa therapy resulted in lowering of TGF-betaRs as well as Smad4 and pSmad3, with concurrent increased in Smad7 expression in both leiomyoma and myometrium compared to untreated group (P<0.05). Immunohistochemically Smads and pSmad3 were localized in cytoplasmic/nuclear compartments of leiomyoma and myometrial smooth muscle cells and connective tissue fibroblasts, with alteration in their intensity (HScores) in GnRHa-treated group. In conclusion, the results indicates that leiomyoma and myometrium express all the components of TGF-betaR and Smads, and GnRHa therapy results in alteration of their expression further supporting the importance of TGF-beta system as key regulator of leiomyoma growth.