Two in vivo experiments are described in the study. In the first one the biocompatibility and tissue reaction to glass and glass-ceramic biomaterials implanted into the rat skeletal muscle was examined. Four types of biomaterials were tested: bioglasses of new generation Sz2 and A2, and classical bioglasses based on Hench's bioceramics. The results of the experiment demonstrated the biocompatibility of all four materials but higher bioactivity was stated in the case of bioglasses A2 and Sz2. The objective of the second experiment was to investigate the effect of the new generation bioglass Sz2 (c ho sen on the base of previous study) on bone regeneration. The study was performed on 50 rabbits. Defects made in radius of both limbs were filled with bioglass Sz2 or inert glass Si02 used as a control. After 3, 7, 21, 42 and 90 days from the surgery, animals were killed and fragments of bone containing implants were excised and processed for the examination in light microscopy. The activity of enzymes important for the bone tumover was detected histochemically. The presence of calcium deposits was analysed by Alizarin Red S (ARS) staining. In all samples with implanted bioglass there was a significant increase in the activity of enzymes and in the percentage of ARS labelled tissue surface when compared to samples with Si02 (p≤S0.05). Consequently, the new bone forming was observed m ; uch often around bioglass implants. The results demonstrate the suitability of bioactive glass Sz2 as a scaffold for bone tissue engineering as it not only stimulates the activity of cells, but also provides an steoconductive and osteoproductive substrate.