Toluene is one of the BTEX (benzene, toluene, ethylbenzene, and xylenes) which, also known as methylbenzene is a clear, water-insoluble liquid with the typical smell of paint thinners, redolent of the sweet smell of the related compounds benzene. Toluene is an aromatic hydrocarbon which is widely used as an industrial feedstock as a solvent. Trichloroethylene (TCE) is a chlorinated aliphatic hydrocarbon (CAH) that has been widely used as an ingredient in industrial cleaning. TCE is one of the most frequently detected contaminants in groundwater which considered as a suspected carcinogen. Trichloroethylene (TCE) can be co-metabolic degraded under aerobic condition using toluene as growth substrate. Study of Burkholderia vietnamiensis G4 has demonstrated aerobic co-metabolic TCE degradation. Using bioremediation technology to remove TCE is considered as a cost-effective method compared to chemical treatment. vii The objective of this study is to investigate the bioremoval kinetics of toluene/TCE mixture using B. vietnaiensis G4. Studies were performed on different parameters (toluene/TCE concentrations, microbial inoculation amount, hydrogen peroxide concentration and percentage of powdered activated carbon). Different toluene concentrations at 20, 50 mg/L and TCE concentration at 0.2 mg/L were used. Microbial inoculation amount with initial optical density 1 and 3 were used. DO concentrations caused by hydrogen peroxide and PAC 1% & 3% (w/v) were considered. Depending on the conditions, specific growth rate and half saturation constant were considered to analyze the bioremoval kinetics. Investigating the kinetics of contaminates with their detailed fates/behaviors during bio-removal process is essential even before the remediation technology can be applied on site for the successful remediation of contaminated environment. Since the kinetics of cometabolism are not entirely understood and can be quite complex, this kind of study can be good candidates for bioremediation of the wastes-contaminated sites.