The complexity of software systems makes design reuse a necessary task in the software development process. CASE tools can provide cognitive assistance in this task, helping the software engineers to select designs to be reused. In this paper, we propose an approach for case indexing and retrieval based on Bayesian Networks, Case-Based Reasoning and WordNet. This approach is integrated in a CASE tool that reuses UML class diagrams, providing cognitive help for the software design phase. 1 Motivations Software design [1] is a complex task involving the modelization of software systems representing the world around us. Despite the design guidelines described in software engineering methodologies, designers still rely on experience to build the system model. The experience level often distinguishes good designers from average ones. A possible solution to overcome the lack of experience is to reuse software [2, 3]. Reuse enables more efficient development of software systems, because the d...