Emission properties of 2.0 mu m fluorescence and the energy transfer between Ho3+ and Tm3+ in 57PbO . 25Bi(2)O(2). 18Ga(2)O(3) (mol%) glass codoped with Ho3+ and Tm3+ were investigated. Cross-relaxation rates in Tm3+ increased approximately 5 times when the Tm2O3 concentration was increased from 1.0 to 1.5 wt%. Coefficients of the forward Tm3+ --> Ho3+ energy transfer were about 15 times larger than those of the Tm3+ <-- Ho3+ backward transfer. Analysis of the energy transfer and gain spectra indicated that the highest gain at the 2.0 pm wavelength region could be achieved from the glass with 1.5 wt% of Tm2O3 and 0.3 wt% of Ho2O3.