In this work we present a case study for legacy systems reengineering using software patterns aiming at both easing the reengineering process and improving future maintenance. The approach used consists basically of three steps: apply reverse engineering, if necessary, to obtain an object model of the system; recognize software patterns present in the object model obtained; and re-implement the system in a more productive way, using toolkits or specific frameworks that implement the patterns found. Results of some experiments show that reengineering has been facilitated as well as system maintenance, because components became clearly delimited and larger chunks of design may now be understood as a whole and reused.