Three dimensional assemblies of fibers made from bioactive glass compositions were investigated to determine their usefulness as scaffolds for the repair and regeneration of hard and soft tissues. The microstructure, properties and in-vivo performance were measured for scaffolds (7mm diameter and 2mm thick) made from an interconnected network of discontinuous fibers of bioactive glasses such as 45S5 and 13-93 that were arranged in a random oriented geometry. Scaffolds, made from fibers whose diameter ranged from approximately 100 up to 300 microns, were implanted subcutaneously in laboratory rats for up to four weeks. Scaffolds comprised of randomly oriented fibers seeded with mesenchymal stem cells prior to implantation contained significant new bone-like material after four weeks in-vivo. No bone-like material was observed in un-seeded scaffolds as expected, but these scaffolds were completely penetrated by new soft tissue with noticeable amounts of new vascularization. Histological staining techniques were used to asses the quality of the infiltrating soft tissue and to identify cells and tissues of interest. Biological staining and scanning electron microscopy back scattered imaging (SEM-BSI) showed new bone tissue had formed throughout the scaffolds seeded with mesenchymal stem cells. Scanning electron microscopy electron dispersive spectroscopy (SEM-EDS) analysis of the cross-section of a 13-93 and 45S5 fiber implanted four weeks was used to measure the compositional change of each fiber type to calcium phosphate, demonstrating the reactivity of both materials in-vivo.