Collisional deactivation rate constants, k5(M) for HBr(Χ1Σ+ ν″=5) by M= H2, N2, CO2, and HBr were obtained using the degenerated stimulated hyper-Raman (OSHR) pumping method in a pumping-probe configuration. High- resolution transient laser induced fluorescence (LIF) was used to detect collisionally relaxed HBr. For M=CO2, an efficient near-resonant 1-1 vibration-to- vibration (V-V) energy exchange was observed. It appeared that the presence of a strong infrared-active vibrational mode was a favorable situation for an efficient V-V energy transfer. A 1-1 resonance exciting the infrared forbidden N2(1←0) vibration was also observed, but it was 2 orders of magnitude smaller than that of CO2. Self-relaxation rate constants of HBr (ν″=5) were measured. Single quantum relaxation accounted for about 70% of the total relaxation out of state ν″=5, and two-quantum relaxation made contributions (25%) to the vibrational relaxation at this vibrational energy. Direct evidence for 2-1 resonance in HBr (ν″=5)+H2 was observed. Initial preparation of HBr (ν″=5) resulted in nearly no population in HBr (ν″=4), but direct population of HBr (ν″=3). Therefore only 2-1 resonant energy transfer was important for H2 relaxation. The state specific rate constant for HBr was obtained by the analysis of the state-to-state relaxation data. It was found that the data could be fitted with one adjustable normaligation parameter using a single-quantum relaxation model, which restricted the rate constant. A strong mass effect on the vibrational relaxation rate constant was observed. A further check of the character of the V-V resonant energy transfer in highly vibrationally excited HBr was the temperature dependence of the rate constants. For M=CO2, the temperature dependence of the 1-1 near-resonant energy transfer rate constats was found to be inverted. In contranst, the temperature dependence of the relaxation rate constants for M= H2 and HBr was normal. For M=N2, a weak but position temperature dependence was found. It suggested that this resonance occurred by a different mechanism compared with that in CO2.