Glasses with compositionxCoO · (0.3–x)Na2O · 0.70B2O3have been prepared over the range 0 ·x· 0.12 containing 1 mol%/2 mol% of V2O5. Electron paramagnetic resonance spectra of VO2+of the glasses have been measured at X-band (v· 9.3 GHz) at room temperature. Spin Hamiltonian parameters of the VO2+ions have been calculated. It is found that forx· 0.05 the octahedral symmetry is reduced when Na2O is replaced by CoO. d.c. conductivity of these samples has also been measured which shows that conductivity decreases and activation energy increases when Na2O is replaced by CoO.