INTRODUCTION: The surface properties of biomaterials have a direct in vitro and in vivo influence on a cell's morphology, migration, orientation and protein synthesis 1,2 . We propose to study the protein expression of rat osteoblasts and human fibroblasts on two different Nickel- Titanium (NiTi) surfaces. The NiTi samples were mechanically polished to obtain two kinds of surface roughness (Ra=0.07 µm for "NiTi 2400" and Ra=0.15 µm for "NiTi 400"). RT-PCR was performed to evaluate the expression of type I collagen and fibronectin for both osteoblasts and fibroblasts; and osteocalcin, osteopontin and osteonectin for osteoblasts. METHODS: Cell Culture: Osteoblasts were obtained after collagenase digestion of neonatal rat calvaria. Fibroblasts were obtained from biopsies of clinically healthy human gingiva. RT-PCR : Total RNA was isolated from cells after 7 days of culture on substrates using the "Qiagen RNeasy" kit. First-Strand cDNA synthesis was performed by RT with 2 µg of total RNA using the Superscript II enzyme with oligo dT12-18