Abstract. A software product line comprises a set of products implementing different configurations of features. The set of valid feature configurations within a product line can be described by a feature model. In some practical situations, a feature configuration needs to be derived in stages by creating a series of successive specializations of the initial feature model. In this paper, we consider the scenario where changes to the feature model due to, for example, the evolution of the product line, need to be propagated to its existing specializations and configurations. After discussing general dimensions of model synchronization, a solution to synchronizing cardinality-based feature models and their specializations and configurations is presented.