The results of d.c. and a.c. electrical conductivity measurements in BiXGe1 - xO2 (- 0.5x) (where x = 0.13, 0.23, 0.33, 0.47) and BixSi1 - xO2 (- 0.5x) (where x = 0.47, 0.57, 0.67) glasses are reported and analysed with the aim of understanding the conduction mechanism. A suggestion is given that the electric conductivity in these glasses can be interpreted by single ionic mechanism. An explanation of a pronounced increase in conductivity for x>0.33 was proposed on the basis of percolation in high mobility BiO5-6 network.