Biological treatability of major agro-industries wastewaters, such as meat processing effluents can only be evaluated with specific emphasis on slowly biodegradable substrate and using a multi-component modelling approach. This paper reviews the framework of the endogenous decay model and summarizes the necessary COD fractionation and the kinetic information to be incorporated in this model as applied to a meat processing effluent. Model interpretations of the respirometric experiments are used to define the fate of slowly biodegradable GOD. Behavior of this wastewater in continuous activated sludge systems is studied by model simulations based upon experimental results. Copyright (C) IAWQ 1996. Published by Elsevier Science Ltd.