Software maintenance is widely known as a problematic area that may consume up to 80% of a software project?s resources. It has been claimed that providing an effective mechanism to access Design Rationale (DR) has great potential to improve software maintenance processes. However, we postulate that the first step towards exploring the potential of DR for improving software maintenance should be to gain a better understanding of what DR means to practitioners, how valuable they consider DR to be and how they use DR. To determine the perceived usefulness of DR, we surveyed a large number of software designers. This exploratory study has discovered that practitioners recognize the importance of DR to understand existing designs and frequently use it to reason about proposed modifications. The results of this study establish that DR is perceived by practitioners to be useful and the efforts required to capture DR for the purpose of maintenance are worthwhile. The findings allow us to identify areas of further research on DR support that have the potential to improve the maintenance process.