Abstract The complexity associated to naturally fractured formations constrain reservoir engineers to use simplified versions of the material balance equation for determining the initial hidrocarbon in place and predicting reservoir performance. This work presents a new material balance equation for naturally fractured reservoirs, wich is presented by complementing a mathematical model introduced by Peñuela et al 2001, that considers a porous medium composed of interdependent matrix and fracture system. By including both dissolved gas and volatilized oil was able to overcome the long standing limitations of the material balance in naturally fractured reservoirs resulting a unique material balance equation wich was applicable to full range of reservoir fluids –including volatile oils and gas condensates. The proposed equation extend the equations presented by Peñuela et al 2001 and Niz et al 2004, in handling compositional effects of fluid composition in naturally fractured reservoirs. The new equation can be shown to degenerate to preexisting methods under appropiate reservoir conditions. Synthetic examples are given to validate the approach and illustrate how to apply this method in compositional and no compositional reservoirs. All previously published works become subsets of the present method.