Apatite-wollastonite (A-W)/high-density polyethylene composite (AWPEX) materials have been designed to match the mechanical strength of human cortical bone and to provide favorable bioactivity, with potential use in many orthopaedic applications. To better understand AWPEX properties, the effects of surface finish and ceramic filler size and content on osteoblast-like cell attachment, proliferation, and differentiation were examined. Glass ceramic content was tested at 30 and 50 vol% and median particle size at 4.5 and 7.7 μm. Samples were prepared as 10 × 10 × 1 mm3 tiles with polished or roughened surfaces, sterilized by gamma irradiation (2.5 Mrad), and characterized by SEM, surface energy, and surface profilometry. Saos-2 human osteoblastlike cells were cultured on each surface at an initial concentration of 4500 cells/cm2 in McCoy's medium and incubated at 37C in a humidified atmosphere with 5% CO2 for 1, 3, or 7 days. At each time point, adenosine triphosphate (ATP) and alkaline phosphatase (ALP) levels were measured to assess cell number and osteoblast differentiation. Significant differences were found at 7 days, confirmed by ANOVA post-hoc testing using Bonferroni's correction. Overall, increased exposure of the A-W phase in AWPEX through surface polishing, higher volume fraction, and/or larger particle size, was found to lead to an improved cell response.