In order to characterize Hypoid gear Vibration and Noise, time domain and frequency domain approaches are undertaken with backlash, offset, torque and gear mesh frequency varied. Experiments are performed with three types of gear sets:overlapped, well-lapped and poor-lapped gears. By using a pulse type of trigger signal synchronizing each tooth contact, gear mesh frequency is detected and signal averagings are performed in time domain, corresponding frequency analysis being performed with the aid of a Digital Signal Analyzer. The experimental results show that the parameter effects such as torque, backlash, offset and mesh frequency are clarified by considering the harmonic amplitudes and their ratios and the peak-to-peak amplitude of gear vibration and noise and that the degree of lapping is well discriminated by the 1st and 2nd harmonic amplitude ratio obtained when the mesh frequency is above 180 Hz and the backlash is larger than 0.10 m/m for both clockwise and counterclockwise gear rotation directions.