A novel method for the determination of microbial growth kinetics on hydrophobic volatile organic compounds (VOC) has been developed. A stirred tank reactor was operated as a fed-batch system to which the VOC was continuously fed via the gas phase, assuring a constant VOC concentration in the mineral medium. A flow of air was saturated with the VOC, and then mixed with a further flow of air, to obtain a predetermined VOC concentration. Thus, different VOC concentration; in the mineral medium could be obtained by altering the VOC concentration in the feed gas. The growth kinetics of Xanthobacter autotrophicus GJ10 on 1,2-dichloroethane (DCE) and of Pseudomonas sp. strain JS150 on MonoChloroBenzene (MCB) were assessed using this method. The growth of strain JS150 than 160 mg l(-1) and the results were fitted using a piecewise function. The growth kinetics of strain GJ10 were described by the Luong model where maximum growth rate mu(max) = 0.12 h(-1) substrate saturation constant K-S = 7.8 mg l(-1) and maximum substrate concentration S-m (above which growth is completely inhibited) = 1080 mg l(-1). Varying nitrogen and oxygen hows enabled the effect of oxygen concentration on the growth kinetics of Pseudomonas JS150 to be determined.