This work is a contribution of Artificial Intelligence to Software Engineering. We present a comprehensive approach to metamodel instantiation using CSP. The generation of models which conform to a given metamodel is a crucial issue in Software Engineering, especially when it comes to produce a variate and large dataset of relevant models to test model transformations or to properly design new metamodels. We define an original constraint modeling of the problem of generating a model conform to a metamodel, also taking into account its additional OCL constraints. The generation process we describe appears to be quicker, more efficient and flexible than any other state-of-the-art approach.