In this paper, the adsorption kinetics of gasoline vapor on pitch-based activated carbon is experimentally investigated. The main objective is to explore the effect of initial bed pressure on the adsorption rate. The experiments have been conducted by using a thermogravimetric analyzer (TGA) unit, which has a precision of +/- 0.1 mu g in measuring the adsorption uptake, at adsorption temperatures of 30 degrees C and 35 degrees C which are useful for gasoline emission control. Pressure is found to influence the adsorption rate and uptake. The adsorption rate constants or effective mass transfer coefficients are correlated with the pressure differences between the gasoline vapor and the adsorption chamber. This study suggests that the effect of the initial pressure of the adsorption chamber should be taken into account in calculating the adsorption kinetics for the simulation of a practical adsorption process.