This article estimates the pumping performance of a turbobooster vacuum pump (TBP), with spiral-grooved rotor and inner housing, by the computational. fluid dynamics method. The computational domain comprises the flow channels in the rotor and inner housing. Thus, the simulated gas can flow continuously from the inlet of the rotor through the outlet, into the inner housing, and then out the exit port of the pump. The calculations show that the pumping performance of the TBP can be enhanced when the spiral-grooved inner housing is integrated. The spiral angle of the rotor, the groove number, and the spiral angle of the inner housing have to be designed carefully to increase the effective pumping length of the flow channel of the TBP to gain further energy from the rotational energy, overcome the subsequent increased friction force, and increase the pumping performance. The calculations also show that the compression ratio and the pumping speed in this case, which comprises the rotor with five grooves and 15degrees spiral angle and the inner housing with five grooves and 27degrees spiral angle, are the largest among all cases studied in this article. (C) 2003 American Vacuum Society.