The thermal, electrical and structural characterization of yLi(2)O . (1 - y){xBi(2)O(3) . (1 - x)B2O3} (y = 0.4, 0.5) glass system has been investigated. The decrease in T-g with the increase in Bi2O3 content has been attributed to the increasing number of non-bridging oxygen atoms from B-O bonds and also the Bi-O linkage which is relatively weaker. The conductivity vs. Bi2O3 composition curve exhibits two maxima at Bi2O3 content = 0.2 mol% and 0.6 mol% for y = 0.5 compositions. This is interpreted in terms of the mixed-former effect and modification effect of Bi2O3 on this glass system, respectively. For glasses with y = 0.4, conductivity has been slightly enhanced at Bi2O3 content = 0.2 mol% which is due to the mixed-former effect. Results obtained from the XPS studies have shown : 1) for samples with y = 0.5, the number of non-bridging oxygen atoms from B-O bond increases with the increase in Bi2O3 content for composition range 0.2 mol% < Bi2O3 content less than or equal to 0.8 mol% and gets to a maximum value at Bi2O3 content = 0.6 mol% where the conductivity has also exhibited a maximum value. For higher Bi2O3 content (greater than or equal to 1 mol%), O 1s spectra of Bi-O-Bi and Bi-O-B bonds (O 1s(3)) have been separated out. When Bi2O3 content = 20 mol%, O 1s spectrum of Bi-O- (O 1s(4)) has been separated out. 2) for samples with y = 0.4, O 1s(3) could be separated out for Bi2O3 content greater than or equal to 0.6 mol%. It is obvious that in 0.4Li(2)O . 0.6(xBi(2)O(3) . (1 - x)B2O3) system more Li+ ions associate with Bi2O3 and in 0.5Li(2)O . 0.5{xBi(2)O(3)(1 - x)B2O3} system they prefer berate units.