The addition of powdered activated carbon (PAC) to activated sludge (AS) reaction units to enhance removal of specific toxic organic compounds such as phenol and m-cresol using with synthetic wastewater was investigated in bench-scale laboratory system. Adsorbability of test materials were studied along with selected commercial PAC to examine the adsorptive capacity of PAC without biological growth using a gyratory shaker assembly. Several tests were made to determine the removal efficiency of priority pollutants in PAC-AS system. These tests indicated that the PAC-AS system capable of reducing highly concentrated organic priority pollutants to below toxic threshold values. Results from steady-state bioreactor studies showed that the PAC dose, sludge age and PAC concentration in activated sludge mixed liquor are important variables. Adsorption of nonbiodegradable organics by PAC seemed to be the main mechanisms of improved COD removal in the PAC-AS system, the process increased the removal efficiency of COD with ranges of 63 to 97 percent. A simple mathematical model was used to obtain several empirical constants such as alpha, beta, and gamma for both pollutant materials (phenol and m-cresol). They were calculated for phenol as: alpha=0.088, beta=1.12, gamma=0.65 and for m-cresol as alpha = 1.20, beta = 0.86, gamma = 1.67. When using these constants in the model equation, they may help to pl edict the performance of PAC-AS system in the presence of priority pollutants.