The facilitative effect of expertise in hypertext information retrieval (IR) tasks has been widely reported in related literature. However, recent theories of human expertise question the robustness of this result, since previous works have not fully considered the interaction between user and system characteristics. In this study, the constraint attunement hypothesis (CAH) is considered in order to predict that the effect of expertise in IR would appear only when the user and system characteristics can be combined successfully. Results from an experiment revealed that expert users outperformed novice users in IR when the elements of a system interface are organized semantically, but not when organized randomly. Results are discussed in the framework of the CAH supporting the interactive nature of human behaviour in HCI. (Contains 1 table and 1 figure.)