A CaO-P(2)O(5)-SiO(2)-ZnO bioglass was formed by the sol-gel technique and characterized by Raman spectroscopy, X-ray diffraction, energy dispersive X-ray analysis (EDXA) and scanning electron microscopy (SEM). The surface reactivity of the resultant glass-ceramic specimens was analyzed by immersion studies in simulated body fluid (SBF). SEM-EDXS and inductively coupled plasma atomic emission spectrometry techniques were used to monitor changes in the glass surface and SBF composition. Osteoblast cell culture experiments were performed to assess the biocompatibility and the alkaline phosphatase activity. Cell counts of the osteoblasts cultured on the bioglass samples were studied and compared with the polystyrene plates. The cells cultured on the bioglass disks consistently showed a higher alkaline phosphatase activity and cell counts compared to cells cultured on either polystyrene plates or the base CaO-P(2)O(5)-SiO(2) bioglass. This was due to cell proliferation and differentiation promoted by the zinc-substituted bioglass.