Abstract In complex environments it is important that action is directed towards relevant information. This thesis investigates the role of objects in inhibitory mechanisms of visual attention. It is critical for humans and other animals to search the environment efficiently. Posner and colleagues (1984,1985) demonstrated that inhibition of the return (IOR) of attention ensures the movement of attention to new locations. Subsequent research suggested that this inhibition could be associated with objects and that object-based representations support efficient visual search over long delays and intervening events. The present series of experiments investigated the role of object-based representations in IOR. The results confirmed previous work showing long-term IOR for faces, and also demonstrated, for the first time, long-term IOR for non-face objects. Long-tenn IOR occurred even when cues and targets were identical, suggesting that this effect is due to retrieval of object-based inhibition, not mismatching perceptual information. These results suggest that inhibitory processing states associated with objects can be encoded into memory, and subsequently retrieved when the object reappears. Further experiments found that IOR is mediated by object identity but not object category. IOR over short intervals was associated with the identity of realistic objects, as well as the identity of meaningless shapes, but there was no evidence to suggest that IOR could be associated with an object's category. Long-term IOR was also associated with object-identity and not with object category. However, no long-term IOR was observed for identical meaningless shapes, which suggests that memory encoding and retrieval of IOR can only occur if the inhibition is associated with the identity of meaningful objects. The final experimentg provided further evidence for the role of object-based representations in IOR by showing that IOR can be influenced by action-related properties of objects. Taken together, the results of this research show that IOR can be relatively long lasting and is mediated by complex identity-based representations of objects.