The biodegradation kinetics of BTEX (benzene, toluene, ethylbenzene and xylene isomers) compounds were studied individually and as mixtures by using models with different levels of sophistication. In order to evaluate the performances of the unstructured models we used experimental data from literature. The system description was based on the material balances of key components for batch operations, where Monod and Andrews models were applied for the biodegradation of individual substrates. To simulate the biodegradation kinetics of substrate mixtures, models of competitive, noncompetitive and uncompetitive inhibition were applied along with the sum kinetics with interaction parameters (SKIP) models. The kinetic parameters were estimated via a global search method known as Particle Swarm Optimization (PSO). The main result of this study shows that the sophisticated biodegradation kinetics of BTEX mixtures can be successfully described by applying a SKIP model, with the main advantage being the consideration of the substrate interactions. (C) 2010 Elsevier Ltd. All rights reserved.