The aim of this study was to evaluate the cytocompatibility, cell ingrowth and extracellular matrix deposition of a newly developed porous bioactive glass as a bone substitute. Two types of bioactive glass, different in their pore size (75 and 20 ppi, resp. ~350 and ~1200 $m), were used in this study. The materials were seeded with human osteoblastic (MG63) and fibroblastic (M-228 F01 and M-191 F01) cell lines. The cells were visualized by two techniques, scanning electron microscopy and confocal microscopy. For confocal microscopy cell nuclei were labeled with propidium iodide (IP) and the extracellular matrix components (type I collagen and osteocalcin) by specific antibodies. Cells and matrix were visualized by fluorescence. The bioactive glass used in this study was shown to be non cytotoxic. Cell growth and colonization at the surface and in the depth of the material were observed. Extracellular matrix deposition was also demonstrated which proved the proper biofunctionality of the biomaterial. Scanning electron microscope allowed us to visualize cells at a high magnification at the surface of the bioglass and evidenced that the biomaterials were covered by a sheet of cells with their matrix; on the other hand, confocal microscopy permitted us to observe cell ingrowth and matrix deposition within the depth of the substitute. We showed that extracellular matrix was synthesized mainly in the upper levels where the cell population was the most confluent. In summary, this porous bioglass appears promising for bone substitution.