In this study, we have investigated calcium and silicate-free samples over a wide compositional range in the xB2O3·30 Na2O·(70−x)P2O5 system, with 0 ≤ x ≤ 70 mol%, in order to determine the influence of the chemical composition on their structure and bioactive response in simulated body fluid. Information related to the chemical structures present in the network was obtained by means of Raman and infrared spectroscopy. For samples containing small amounts of P2O5, boron structures are preponderant. Upon increasing the phosphorus content, the samples' network is based on phosphate chains linked by boron groups through ‘P–O–B’ bridges. For high concentration of P2O5, the Q3 units form three-dimensional network, whereas Q2 units assist the chain formation. Regarding the in vitro assessment of bioactivity, the clear print of PO4 asymmetric bending vibrations of apatite-like layer in the 540–680 cm−1 spectral domain, the scanning electron micrographs and energy dispersive x-ray analysis spectra demonstrate that the studied borophosphate samples exhibit good bioactive response only for certain chemical compositions. More exactly, the highest bioactivity is obtained for 30% and 20% B2O3 (mol%) after 3 and 11 days of immersion, respectively. Therefore, the samples with 20–30 mol% boron content are valuable candidates that can be used as materials for tissue engineering applications. Copyright © 2013 John Wiley & Sons, Ltd.