Independently of the type of maintenance carried out, regression testing activities are mandatory to test the modifications and the eventual new features. They are also required to check whether the existent features were not adversely affected by the modifications. Many techniques have been proposed to reduce the efforts and to increase the effectiveness of the regression testing activities. Empirical studies are necessary to evaluate and compare these techniques. In this paper, we report a case study that aims at evaluating and comparing the application of two promising regression testing techniques: one based on modification and the other based on selective mutation. The accomplishment of this study contributes towards the establishment of effective, low cost regression testing strategies.