This paper presents a prediction method for the evaluation of bistatic intersystem interference due to rain scatter, associated with a physical model of the meteorological environment. The precipitation phenomena are modeled through a population of isolated three-dimensional rain cells, with exponential rain rate profile inside; each cell is characterized by a specific value of size and peak rain intensity. Starting from the complete bistatic radar equation (BRE), a simplified expression is obtained that can often be used and that preserves accuracy when computing time is at premium. The limits of applicability of the simplifications above are identified and throughly discussed. The model is then successfully validated against the database of experimental measurements, collected in the framework of the COST (European Cooperation in the Fields of Scientific and Technical Research) 210 project <Commission of the European Communities, 1991>. The importance of being able to evaluate propagation quantities (e.g., transmission loss, attenuation) jointly is also stressed: Quite often the transmission loss statistic alone, in fact, is not sufficient to characterize the interference problem.¿ 1997 American Geophysical Union