Titanium (Ti) surfaces with rough microtopographies enhance osteogenic differentiation, local factor production, and response to osteogenic agents in vitro and increase pullout strength of dental implants in vivo. Estrogens regulate bone formation, resorption, and remodeling in females and may be important in implant success. Here, we tested the hypothesis that estrogen modulates osteoblast response to implant surface morphology. Primary female human osteoblasts were cultured to confluence on three Ti surfaces (pretreatment, PT -R a 0.60 m; sandblasted and acid-etched, SLA -R a 3.97 m; and Ti plasma-sprayed, TPS -R a 5.21 m) and treated for 24 h with 10 −7 or 10 −8 M 17␤-estradiol (E 2 ). Cell number decreased with increasing surface roughness, but was not sensitive to E 2 . Alkaline phosphatase specific activity of isolated cells and cell layer lysates was lower on rough surfaces. E 2 increased both parameters on smooth surfaces, whereas on rough surfaces, the stimulatory effect of E 2 on alkaline phosphatase was evident only when measuring cell layer lysates. Osteocalcin levels were higher in the conditioned media of cells grown on rough surfaces; E 2 had no effect in cultures on the plastic surfaces, but increased osteocalcin production on all Ti surfaces. TGF-␤1 and PGE 2 production was increased on rough surfaces, and E 2 augmented this effect in a synergistic manner; on smooth surfaces, there was no change in production with E 2 . The response of osteoblasts to surface topography was modulated by E 2 . On smooth surfaces, E 2 affected only alkaline phosphatase, but on rough surfaces, E 2 increased levels of osteocalcin, TGF-␤1, and PGE 2 . These results show that normal adult human female osteoblasts are sensitive to surface microtopography and that E 2 can alter this response.