In vitro bioactivity of borate glasses with composition xNa2xCaO·2xB2O3 (where x is in wt%=24.8, 24.2, 23.8, 23.2) containing 0, 2, 4, 6 wt% P2O5 has been investigated by soaking them in a simulating body fluid (SBF) up to 15 days at 37°C. Investigation of glass degradation is carried out by taking percentage weight loss in SBF and by measuring the pH of SBF as a function of time. Inductively coupled plasma emission spectroscopy is used to study the ionic concentration of BIII, CaII, and NaI ions in SBF after 15 days of assay. Fourier transform infrared spectra are taken before and after dipping in SBF for structural analysis and for confirmation of hydroxyl carbonate apatite layer formation in SBF after 15 days. The results show that P2O5 plays an important role in controlling chemical durability and bioactivity. A borate glass with the same composition as 45S5 bioglass prepared by Hench but with SiO2 replaced by B2O3 in weight percentage has been prepared for comparison of bioactivity for the two.