einsurance offers insurance companies many advantages, including stabilization of losses and surplus enhancement, according to Outreville (chapter 3, this volume). Can reinsurance therefore ensure the financial stabilization of multiple microinsurance units? This question can be approached in two ways: empirically or theoretically. The empirical approach consists of carrying out repeated field studies in real-life settings and observing the results. However, since there are no field data on reinsurance transactions with microinsurers, whether reinsurance can work for small health schemes needs to be assessed through theoretical reasoning. The theoretical approach is based on identifying qualitative information concerning possible solutions, through simplified representations of the problem (the model), and then defining a calculation protocol to validate (or invalidate) the model's underlying hypothesis through the results (Lesage 1999). This chapter describes the theoretical approach followed in the model. This model tests the hypothesis that microinsurance schemes, operating on their own, are financially less viable than they would be if they pooled their risks through reinsurance. This proof entails consideration of three subissues: * Demonstration of the positive effect of reinsurance on microinsurers' financial viability * Exploration of the utility of reinsurance for microinsurers and the variables affecting their decision to reinsure * Elaboration of a protocol for calculating the reinsurance premium, based on analysis of scenarios that are likely to occur in reality