Alkali-treated titanium surfaces have earlier shown to induce bone-like apatite deposition. In the present study, the effect of surface topography of two-dimensional and pore architecture of three-dimensional alkali-treated titanium substrates on the in vitro bioactivity was investigated. Titanium plates with a surface roughness of R-a = 0.13 mu m, 0.56 mu m, 0.83 mu m, and 3.63 mu m were prepared by Al2O3 grit-blasting. Simple tetragonal and face-centered Ti6Al4V scaffolds with spatial gaps of 450-1100 mu m and 200-700 mu m, respectively, were fabricated by a three-dimensional fiber deposition (3DFD) technique. After alkali treatment, the titanium plates with a surface roughness of R-a = 0.56 mu m were completely covered with hydroxyapatite globules after 7 days in simulated body fluid (SBF), while the coverage of the samples with other surface roughness values remained incomplete. Similarly, face-centered Ti6Al4 scaffolds with spatial gaps of 200-700 mu m exhibited a full surface coverage after 21 days in SBF, while simple tetragonal scaffolds with spatial gaps of 450-1100 mu m were only covered for 45-65%. This indicates the importance of surface topography and pore architecture for in vitro bioactivity. (C) 2010 Elsevier B.V. All rights reserved.