2766 20160701171710.0 ASTROimport-923 Volpi, D. 2012 Massive Non-Thermal Radio Emitters: New Data and their Modeling During recent years some non-thermal radio emitting OB stars have been discovered to be binary or multiple systems. The non-thermal emission is due to synchrotron radiation that is emitted by electrons accelerated up to high energies. The electron acceleration occurs at the strong shocks created by the collision of radiatively-driven winds. Here we summarize the available radio data and more recent observations for the binary Cyg OB2 No. 9. We also show a new emission model which is being developed to compare the theoretical total radio flux and the spectral index with the observed radio light curves. This comparison will be useful in order to solve fundamental questions, such as the determination of the stellar mass-loss rates, which are perturbed by clumping. Blomme, R. De Becker, M. Nazé, Y. Proceedings of a Scientific Meeting in Honor of Anthony F. J. Moffat 465 2012 369 http://esoads.eso.org/abs/2012ASPC..465..369V published in NONREF