A common property of practically all multi-party key agreement protocols is that they are non-hierarchical, i.e., they do not support user hierarchies. However, in real life, it is likely that members of groups and organizations differ in ranking according to their job positions so that people of higher rankings are privileged the same and higher privileged information than people of lower rankings. Hierarchical access control schemes address this issue, but they assume rather fixed scenarios based on centralized key distribution with predefined root keys and key parameters set by a trusted center. In this paper, we propose a decentralized efficient hierarchical multi-party key agreement protocol well-suited for ad-hoc wireless networks that ensures secure user hierarchies.