A theoretical model for the electromagnetic field within a reverberating chamber in presence of an unstirred component is presented. Due to the stochastic nature of the electromagnetic field within the chamber, a statistical electromagnetic approach is developed and tested versus measurements. On the theoretical side, such a physical model is representative of many complex electromagnetic environmental situations, e.g., urban environments, and, therefore, it is of great relevance in the EMC field. On the applicative side, the model can be furthered in order to characterize a reverberating chamber whether it is well operated or not and to set up an environment with a specific amount of direct coupling in conjunction with a stochastic field.