Abstract: One of the most important problems in the evolution of legacy systems is the lack of knowledge about them. Since their documentation is usually outdated, the most reliable source of information for recovering this knowledge is the structure and behavior of the information system itself. In this work, we present an approach for extracting structural business rules from legacy databases. Based on the OMG SBVR standard, we defined a mapping between database and business rules components, implemented the mapping in a rule extraction tool and used it in a financial legacy information system. As a result, we extracted 756 structural business rules. The evaluation of the approach indicates that the proposed mapping is appropriate in terms of the number of real extracted business rules, resulting in around 85% of accuracy.